Remove feature flag `introduce_marker_ranges`

* Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/324068
* Original implementation: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/55669

Changelog: changed

config/feature_flags/development/introduce_marker_ranges.yml

----
-name: introduce_marker_ranges
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/55669
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/324068
-milestone: '13.10'
-type: development
-group: group::source code
-default_enabled: false

lib/gitlab/diff/highlight.rb

@@ -70,12 +70,6 @@ module Gitlab
         return rich_line if marker_ranges.blank?
 
         begin
-          # MarkerRange objects are converted to Ranges to keep the previous behavior
-          # Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/324068
-          if Feature.disabled?(:introduce_marker_ranges, project, default_enabled: :yaml)
-            marker_ranges = marker_ranges.map { |marker_range| marker_range.to_range }
-          end
-
           InlineDiffMarker.new(diff_line.text, rich_line).mark(marker_ranges)
         # This should only happen when the encoding of the diff doesn't
         # match the blob, which is a bug. But we shouldn't fail to render

lib/gitlab/diff/highlight_cache.rb

@@ -74,7 +74,6 @@ module Gitlab
             diffable.cache_key,
             VERSION,
             diff_options,
-            Feature.enabled?(:introduce_marker_ranges, diffable.project, default_enabled: :yaml),
             Feature.enabled?(:use_marker_ranges, diffable.project, default_enabled: :yaml),
             Feature.enabled?(:diff_line_syntax_highlighting, diffable.project, default_enabled: :yaml)
           ].join(":")

spec/lib/gitlab/diff/highlight_cache_spec.rb

@@ -238,17 +238,7 @@ RSpec.describe Gitlab::Diff::HighlightCache, :clean_gitlab_redis_cache do
     subject { cache.key }
 
     it 'returns cache key' do
-      is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:true:true:true")
-    end
-
-    context 'when the `introduce_marker_ranges` feature flag is disabled' do
-      before do
-        stub_feature_flags(introduce_marker_ranges: false)
-      end
-
-      it 'returns the original version of the cache' do
-        is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:false:true:true")
-      end
+      is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:true:true")
     end
 
     context 'when the `use_marker_ranges` feature flag is disabled' do
@@ -257,7 +247,7 @@ RSpec.describe Gitlab::Diff::HighlightCache, :clean_gitlab_redis_cache do
       end
 
       it 'returns the original version of the cache' do
-        is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:true:false:true")
+        is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:false:true")
       end
     end
 
@@ -267,7 +257,7 @@ RSpec.describe Gitlab::Diff::HighlightCache, :clean_gitlab_redis_cache do
       end
 
       it 'returns the original version of the cache' do
-        is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:true:true:false")
+        is_expected.to eq("highlighted-diff-files:#{cache.diffable.cache_key}:2:#{cache.diff_options}:true:false")
       end
     end
   end

spec/lib/gitlab/diff/highlight_spec.rb

@@ -56,26 +56,6 @@ RSpec.describe Gitlab::Diff::Highlight do
         expect(subject[5].rich_text).to eq(code)
       end
 
-      context 'when introduce_marker_ranges is false' do
-        before do
-          stub_feature_flags(introduce_marker_ranges: false)
-        end
-
-        it 'keeps the old bevavior (without mode classes)' do
-          code = %Q{+<span id="LC9" class="line" lang="ruby">      <span class="k">raise</span> <span class="no"><span class="idiff left">RuntimeError</span></span><span class="p"><span class="idiff">,</span></span><span class="idiff right"> </span><span class="s2">"System commands must be given as an array of strings"</span></span>\n}
-
-          expect(subject[5].rich_text).to eq(code)
-        end
-
-        context 'when use_marker_ranges feature flag is false too' do
-          it 'does not affect the result' do
-            code = %Q{+<span id="LC9" class="line" lang="ruby">      <span class="k">raise</span> <span class="no"><span class="idiff left">RuntimeError</span></span><span class="p"><span class="idiff">,</span></span><span class="idiff right"> </span><span class="s2">"System commands must be given as an array of strings"</span></span>\n}
-
-            expect(subject[5].rich_text).to eq(code)
-          end
-        end
-      end
-
       context 'when no diff_refs' do
         before do
           allow(diff_file).to receive(:diff_refs).and_return(nil)