[rich-text] Improve toolbar button styles (#11419)

GitOrigin-RevId: 81def8f65591fe9f8f914384db971238faa4483f

services/web/frontend/stylesheets/app/editor/toolbar.less

@@ -341,9 +341,12 @@
 }
 
 .formatting-buttons-cm6-panel {
-  padding-top: 4px;
   background-color: @formatting-btn-bg;
   display: flex;
+
+  & .formatting-btn {
+    padding: 2px 0;
+  }
 }
 
 .formatting-btn {