Update Ruby detection rules for SAST

Now that brakeman supports scanning any Ruby file, update detection
logic to scan any Ruby project, not just Rails projects.

changelogs/unreleased/rf-update-brakeman-rules.yml

+---
+title: Update Ruby detection rules for SAST
+merge_request: 53414
+author:
+type: changed

lib/gitlab/ci/templates/Security/SAST.gitlab-ci.yml

@@ -66,7 +66,8 @@ brakeman-sast:
     - if: $CI_COMMIT_BRANCH &&
           $SAST_DEFAULT_ANALYZERS =~ /brakeman/
       exists:
-        - 'config/routes.rb'
+        - '**/*.rb'
+        - '**/Gemfile'
 
 eslint-sast:
   extends: .sast-analyzer

spec/services/ci/create_pipeline_service_spec.rb

@@ -538,7 +538,7 @@ RSpec.describe Ci::CreatePipelineService do
         it 'pull it from Auto-DevOps' do
           pipeline = execute_service
           expect(pipeline).to be_auto_devops_source
-          expect(pipeline.builds.map(&:name)).to match_array(%w[build code_quality eslint-sast secret_detection_default_branch test])
+          expect(pipeline.builds.map(&:name)).to match_array(%w[brakeman-sast build code_quality eslint-sast secret_detection_default_branch test])
         end
       end