Remnove simplified build group name feature flag

- Add Changelog entry
- Remove old docs
- Remove old implementation
- Remove feature flag defintion

app/models/commit_status.rb

@@ -210,26 +210,7 @@ class CommitStatus < ApplicationRecord
   end
 
   def group_name
-    simplified_commit_status_group_name_feature_flag = Gitlab::SafeRequestStore.fetch("project:#{project_id}:simplified_commit_status_group_name") do
-      Feature.enabled?(:simplified_commit_status_group_name, project, default_enabled: false)
-    end
-
-    if simplified_commit_status_group_name_feature_flag
-      # Only remove one or more [...] "X/Y" "X Y" from the end of build names.
-      # More about the regular expression logic: https://docs.gitlab.com/ee/ci/jobs/#group-jobs-in-a-pipeline
-
-      name.to_s.sub(%r{([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z}, '').strip
-    else
-      # Prior implementation, remove [...] "X/Y" "X Y" from the beginning and middle of build names
-      # 'rspec:linux: 1/10' => 'rspec:linux'
-      common_name = name.to_s.gsub(%r{\b\d+[\s:\/\\]+\d+\s*}, '')
-
-      # 'rspec:linux: [aws, max memory]' => 'rspec:linux', 'rspec:linux: [aws]' => 'rspec:linux'
-      common_name.gsub!(%r{: \[.*\]\s*\z}, '')
-
-      common_name.strip!
-      common_name
-    end
+    name.to_s.sub(%r{([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z}, '').strip
   end
 
   def failed_but_allowed?

changelogs/unreleased/fix-build-group-name.yml

++---
++title: Simplify Build Group name correction
++merge_request:
++author:
++type: fixed

config/feature_flags/development/simplified_commit_status_group_name.yml

----
-name: simplified_commit_status_group_name
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52644
-rollout_issue_url:
-milestone: '13.9'
-type: development
-group: group::testing
-default_enabled: false

doc/ci/jobs/index.md

@@ -137,24 +137,11 @@ The jobs are ordered by comparing the numbers from left to right. You
 usually want the first number to be the index and the second number to be the total.
 
 [This regular expression](https://gitlab.com/gitlab-org/gitlab/blob/2f3dc314f42dbd79813e6251792853bc231e69dd/app/models/commit_status.rb#L99)
-evaluates the job names: `\d+[\s:\/\\]+\d+\s*`.
+evaluates the job names: `([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z`.
 
-### Improved job grouping
-
-> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52644) in GitLab 13.9.
-> - It's [deployed behind a feature flag](../../user/feature_flags.md), disabled by default.
-> - It's enabled on GitLab.com.
-> - To use it in GitLab self-managed instances, ask a GitLab administrator to [enable it](../../administration/feature_flags.md). **(FREE SELF)**
-
-Job grouping is evaluated with an improved regular expression to group jobs by name:
-
-- `([\b\s:]+((\[.*\])|(\d+[\s:\/\\]+\d+)))+\s*\z`.
-
-The new implementation removes one or more `: [...]`, `X Y`, `X/Y`, or `X\Y` sequences
-from the **end** of job names only.
-
-Matching substrings occurring at the beginning or in the middle of build names are
-no longer removed.
+It removes one or more `: [...]`, `X Y`, `X/Y`, or `X\Y` sequences
+from the **end** of job names only. Matching substrings occurring
+at the beginning or in the middle of build names are not removed.
 
 ## Specifying variables when running manual jobs