[NTP] Image overflow bug fix

Fixes an image overflow issue on the NTP page that causes scroll bars
to appear on the animated image / doodle.

(cherry picked from commit b31e0cf)

Bug: 1317403
Change-Id: Id92e2fa7a73198666a9ccedf4eb8b4e5d28948a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3593931
Reviewed-by: John Lee <johntlee@chromium.org>
Commit-Queue: Roman Arora <romanarora@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#993840}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3607300
Cr-Commit-Position: refs/branch-heads/5005@{#173}
Cr-Branched-From: 5b4d945-refs/heads/main@{#992738}

chrome/browser/resources/new_tab_page/untrusted/image.html

@@ -9,7 +9,8 @@
       }
 
       body {
-        margin: 0
+        margin: 0;
+        overflow: hidden;
       }
 
       img {