message: tweak the message menu cancel icon size
diff: @@ -58,7 +58,12 @@ limitations under the License.
  }
  .mx_MessageContextMenu_iconCancel::before {
  + height: 12px;
  + left: 2px;
  mask-image: url('$(res)/img/cancel.svg');
  + position: relative;
  + top: 2px;
  + width: 12px;
  }
  .mx_MessageContextMenu_iconRedact::before {
  