Merge branch 'slashmanov/fix-merge-request-tabs-background-leak' into 'master'

Fix merge request tabs background leakage

See merge request gitlab-org/gitlab!80612

app/assets/stylesheets/pages/merge_requests.scss

@@ -218,6 +218,10 @@ $tabs-holder-z-index: 250;
 .epic-tabs-holder {
   top: $header-height;
   z-index: $tabs-holder-z-index;
+  margin-left: -$gl-padding;
+  margin-right: -$gl-padding;
+  padding-left: $gl-padding;
+  padding-right: $gl-padding;
   background-color: $body-bg;
   border-bottom: 1px solid $border-color;