Link from android-binary-size docs -> gerrit plugin

Change-Id: I532b9e054a047bffa34fddaee6e69c2b0795b204
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391215
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804416}

docs/speed/binary_size/android_binary_size_trybot.md

@@ -207,3 +207,4 @@ For more information on when to use `const char *` vs `const char[]`, see
 
 - [Link to recipe](https://cs.chromium.org/chromium/build/scripts/slave/recipes/binary_size_trybot.py)
 - [Link to src-side checks](/tools/binary_size/trybot_commit_size_checker.py)
+- [Link to Gerrit Plugin](https://chromium.googlesource.com/infra/gerrit-plugins/chromium-binary-size/)