Disallow invalid inline style comments in stylesheets (#9099)

res/css/views/rooms/_MessageComposer.pcss

@@ -75,8 +75,8 @@ limitations under the License.
 .mx_MessageComposer_e2eIcon.mx_E2EIcon {
     position: absolute;
     left: 20px;
-    margin-right: 0; // Counteract the E2EIcon class
-    margin-left: 3px; // Counteract the E2EIcon class
+    margin-right: 0; /* Counteract the E2EIcon class */
+    margin-left: 3px; /* Counteract the E2EIcon class */
     width: 12px;
     height: 12px;
 }
@@ -119,8 +119,8 @@ limitations under the License.
     word-break: break-word;
 }
 
-// FIXME: rather unpleasant hack to get rid of <p/> margins.
-// really we should be mixing in markdown-body from gfm.css instead
+/* FIXME: rather unpleasant hack to get rid of <p/> margins. */
+/* really we should be mixing in markdown-body from gfm.css instead */
 .mx_MessageComposer_editor > :first-child {
     margin-top: 0 !important;
 }
@@ -172,7 +172,7 @@ limitations under the License.
 
 .mx_MessageComposer_button_highlight {
     background: rgba($accent, 0.25);
-    // make the icon the accent color too
+    /* make the icon the accent color too */
     &::before {
         background-color: $accent !important;
     }