WebUI Dark Mode: update link color on clean up page, items to remove list

No screenshots cuz I can't easily reproduce.

And yes, this will mildly change the "light mode" (GB 500->700) but I
think it's pretty clear that this UI is emulating a link and therefore
should use the standard link colors.

R=hcarmona@chromium.org
BUG=926658

Change-Id: I6b9cc4697239edea6a165108935acb7ad2e07bff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1501795
Commit-Queue: Dan Beam <dbeam@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Auto-Submit: Dan Beam <dbeam@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637581}

chrome/browser/resources/settings/chrome_cleanup_page/items_to_remove_list.html

@@ -17,7 +17,7 @@
       }
 
       #more-items-link {
-        color: var(--google-blue-500);
+        color: var(--cr-link-color);
         cursor: pointer;
       }