AccountHeader: improve style of DropdownMenu, use Tabler icon

app/soapbox/features/account/components/header.js

@@ -396,7 +396,7 @@ class Header extends ImmutablePureComponent {
 
             <div className='account__header__extra__buttons'>
               <ActionButton account={account} />
-              {me && <DropdownMenuContainer items={menu} icon='ellipsis-v' size={24} direction='right' />}
+              {me && <DropdownMenuContainer items={menu} src={require('@tabler/icons/icons/dots-vertical.svg')} direction='right' />}
             </div>
 
           </div>

app/styles/components/account-header.scss

@@ -197,12 +197,13 @@
 
       .icon-button {
         border: 1px solid var(--brand-color--med);
-        border-radius: 4px;
+        border-radius: 999px;
         box-sizing: content-box;
-        padding: 2px;
+        padding: 7px;
 
-        > div {
-          line-height: 31px !important;
+        .svg-icon {
+          width: 20px;
+          height: 20px;
         }
       }