Removed top border from contribution calendar

Closes #28844

app/assets/stylesheets/framework/calendar.scss

 .calender-block {
-  padding-left: 0;
-  padding-right: 0;
+  padding: 0 0 $gl-padding;
+  border-top: 0;
   direction: rtl;
 
   @media (min-width: $screen-sm-min) and (max-width: $screen-md-max) {

changelogs/unreleased/user-calendar-border.yml

+---
+title: Removed top border from user contribution calendar
+merge_request:
+author: