Merge duplicate CSS selectors

res/css/views/settings/_DevicesPanel.scss

@@ -29,6 +29,7 @@ limitations under the License.
 
 .mx_DevicesPanel_header .mx_DevicesPanel_deviceButtons {
     height: 48px; // make this tall so the table doesn't move down when the delete button appears
+    width: 20%;
 }
 
 .mx_DevicesPanel_header th {
@@ -45,10 +46,6 @@ limitations under the License.
     width: 30%;
 }
 
-.mx_DevicesPanel_header .mx_DevicesPanel_deviceButtons {
-    width: 20%;
-}
-
 .mx_DevicesPanel_device td {
     vertical-align: baseline;
     padding: 0px;