Disallow invalid inline style comments in stylesheets (#9099)

res/css/structures/_NonUrgentToastContainer.pcss

@@ -18,7 +18,7 @@ limitations under the License.
     position: absolute;
     bottom: 30px;
     left: 28px;
-    z-index: 101; // same level as other toasts
+    z-index: 101; /* same level as other toasts */
 
     .mx_NonUrgentToastContainer_toast {
         padding: 10px 12px;
@@ -27,8 +27,8 @@ limitations under the License.
         font-size: $font-13px;
         margin-top: 8px;
 
-        // We don't use variables on the colours because we want it to be the same
-        // in all themes.
+        /* We don't use variables on the colours because we want it to be the same */
+        /* in all themes. */
         background-color: #17191c;
         color: #fff;
     }