Merge branch '66660-follow-up-change' into 'master'

For consistency do not use CSS calc for simple calculation of margin-top

See merge request gitlab-org/gitlab!67270

app/assets/stylesheets/components/whats_new.scss

@@ -36,7 +36,7 @@
 }
 
 .with-performance-bar .whats-new-drawer {
-  margin-top: calc(#{$performance-bar-height} + #{$header-height});
+  margin-top: $performance-bar-height + $header-height;
 }
 
 .with-system-header .whats-new-drawer {