Set user's highlight theme for the Blame page during SSR

Before the change there was no default theme set,
which lead to massive style recalculations.
This change improves Total Blocking Time
by applying user preferred color scheme during server side rendering,
instead of doing it on client after the initial render.

MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/74335
Changelog: other

app/views/projects/blame/show.html.haml

@@ -20,7 +20,7 @@
       %span.legend-box.legend-box-9
       %span.right-label Older
 
-    .table-responsive.file-content.blame.code.js-syntax-highlight
+    .table-responsive.file-content.blame.code{ class: user_color_scheme }
       %table
         - current_line = 1
         - @blame.groups.each do |blame_group|