Remove _RoleButton.pcss (#10958)

* Remove obsolete style rules

These have been obsolete since 3c5c2bef6d.

* Remove _RoleButton.pcss

mx_RoleButton_tooltip style rules are used only on NotificationBadge.tsx.

* Rename the class

res/css/views/rooms/_NotificationBadge.pcss

@@ -69,3 +69,10 @@ limitations under the License.
         }
     }
 }
+
+.mx_NotificationBadge_tooltip {
+    display: inline-block;
+    position: relative;
+    top: -25px;
+    left: 6px;
+}