Merge branch '61640-set-font-size-on-html-not-body' into 'master'

Use rems instead of px to set body font-size

Closes #61640

See merge request gitlab-org/gitlab-ce!28544

app/assets/stylesheets/bootstrap_migration.scss

@@ -22,7 +22,9 @@ body,
 .form-control,
 .search form {
   // Override default font size used in non-csslab UI
-  font-size: 14px;
+  // Use rem to keep default font-size at 14px on body so 1rem still
+  // fits 8px grid, but also allow users to change browser font size
+  font-size: .875rem;
 }
 
 legend {

app/assets/stylesheets/errors.scss

@@ -17,7 +17,7 @@ body {
   text-align: center;
   font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
   margin: auto;
-  font-size: 14px;
+  font-size: .875rem;
 }
 
 h1 {