Enable caching of markdown when viewing blob

app/models/blob_viewer/markup.rb

@@ -14,7 +14,7 @@ module BlobViewer
       {}.tap do |h|
         h[:rendered] = blob.rendered_markup if blob.respond_to?(:rendered_markup)
 
-        if Feature.enabled?(:cached_markdown_blob, blob.project)
+        if Feature.enabled?(:cached_markdown_blob, blob.project, default_enabled: true)
           h[:cache_key] = ['blob', blob.id, 'commit', blob.commit_id]
         end
       end

changelogs/unreleased/263406-enable-cached-markdown-blob-default.yml

+---
+title: Enable caching of markdown when viewing blob
+merge_request: 45367
+author:
+type: performance

config/feature_flags/development/cached_markdown_blob.yml

@@ -4,4 +4,4 @@ introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/44300
 rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/263406
 type: development
 group: group::source code
-default_enabled: false
+default_enabled: true