Merge branch 'sh-disable-diff-instrumentation' into 'master'

Disable method instrumentation for diffs

Closes #52898

See merge request gitlab-org/gitlab-ce!27235

changelogs/unreleased/sh-disable-diff-instrumentation.yml

+---
+title: Disable method instrumentation for diffs
+merge_request: 27235
+author:
+type: performance

config/initializers/zz_metrics.rb

@@ -30,7 +30,6 @@ def instrument_classes(instrumentation)
     # are included.
     %w(app services [^concerns]**) => %w(app services),
     %w(lib gitlab conflicts)       => ['lib'],
-    %w(lib gitlab diff)            => ['lib'],
     %w(lib gitlab email message)   => ['lib'],
     %w(lib gitlab checks)          => ['lib']
   }