Moving margins to a bootstrap class attribute

src/app/+browse-by/+browse-by-metadata-page/browse-by-metadata-page.component.scss

-.browse-by-metadata {
-  margin: 2rem 0 ;
-}
\ No newline at end of file

src/app/shared/comcol-page-browse-by/comcol-page-browse-by.component.html

 <h2 class="comcol-browse-label h5">{{'browse.comcol.head' | translate}}</h2>
-<nav class="comcol-browse" aria-label="Browse Community or Collection" >
+<nav class="comcol-browse mb-4" aria-label="Browse Community or Collection" >
   <div class="list-group list-group-horizontal">
     <a *ngIf="contentType=='collection'" [routerLink]="['/collections/' + id ]" class="list-group-item" routerLinkActive="active">{{'collection.page.browse.recent.head' | translate}}</a>
     <a *ngIf="contentType=='community'" [routerLink]="['/communities/' + id ]" class="list-group-item" routerLinkActive="active" >{{'community.all-lists.head' | translate}}</a>