Disallow invalid inline style comments in stylesheets (#9099)

res/css/views/messages/_ViewSourceEvent.pcss

@@ -19,8 +19,8 @@ limitations under the License.
     opacity: 0.6;
     font-size: $font-12px;
     width: 100%;
-    overflow-x: auto; // Cancel overflow setting of .mx_EventTile_content
-    line-height: normal; // Align with avatar and E2E icon
+    overflow-x: auto; /* Cancel overflow setting of .mx_EventTile_content */
+    line-height: normal; /* Align with avatar and E2E icon */
 
     pre,
     code {
@@ -34,9 +34,9 @@ limitations under the License.
 
     .mx_ViewSourceEvent_toggle {
         visibility: hidden;
-        // override styles from AccessibleButton
+        /* override styles from AccessibleButton */
         border-radius: 0;
-        // icon
+        /* icon */
         mask-repeat: no-repeat;
         mask-position: 0 center;
         mask-size: auto 12px;