Remove gray background from milestone page

Changelog: changed

app/assets/stylesheets/page_bundles/milestone.scss

@@ -7,21 +7,7 @@ $status-box-line-height: 26px;
 }
 
 .milestones {
-  padding: $gl-padding-8;
-  margin-top: $gl-padding-8;
-  border-radius: $border-radius-default;
-  background-color: var(--gray-100, $gray-100);
-
   .milestone {
-    border: 0;
-    padding: $gl-padding-top $gl-padding;
-    border-radius: $border-radius-default;
-    background-color: var(--white, $white);
-
-    &:not(:last-child) {
-      margin-bottom: $gl-padding-4;
-    }
-
     h4 {
       font-weight: $gl-font-weight-bold;
     }