Fix file diff title and renames alignment in discussions

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/31782

The unused toggle was removed previously,
https://gitlab.com/gitlab-org/gitlab-ce/commit/cc37d1dfa11691f2d8357151d4b722b3d114881e#cf11229dd714f7f4b46f102ce6846e25528b6689_7_6

app/views/discussions/_diff_with_notes.html.haml

@@ -2,8 +2,9 @@
 - blob = discussion.blob
 
 .diff-file.file-holder
-  .js-file-title.file-title
-    = render "projects/diffs/file_header", diff_file: diff_file, url: discussion_path(discussion), show_toggle: false
+  .js-file-title.file-title.file-title-flex-parent
+    .file-header-content
+      = render "projects/diffs/file_header", diff_file: diff_file, url: discussion_path(discussion), show_toggle: false
 
   .diff-content.code.js-syntax-highlight
     %table