Remove a TODO about checking `comment-side` in thread elements

All users of gr-diff are using `diff-side` attribute.

Release-Notes: skip
Change-Id: I4d836ebba6eebfb45a2b20ebb874f8743968951b
diff --git a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-utils.ts b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-utils.ts
index 94a7a84..182d48e 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-utils.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff-utils.ts
@@ -146,10 +146,7 @@
 }
 
 export function getSide(threadEl: HTMLElement): Side | undefined {
-  // TODO(dhruvsri): Remove check for comment-side once all users of gr-diff
-  // start setting diff-side
-  const sideAtt =
-    threadEl.getAttribute('diff-side') || threadEl.getAttribute('comment-side');
+  const sideAtt = threadEl.getAttribute('diff-side');
   if (!sideAtt) {
     console.warn('comment thread without side');
     return undefined;