perf: Add link to Android Go bot in documentation

Change-Id: Ibb08b16a76fd89dbdd91cae4f6285d4007a9bf1e
Reviewed-on: https://chromium-review.googlesource.com/1165162Reviewed-by: Ned Nguyen <nednguyen@google.com>
Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581208}

docs/speed/perf_lab_platforms.md

@@ -13,6 +13,7 @@
    7](https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus7v2%20Perf)
  * [Android
    One](https://build.chromium.org/p/chromium.perf/builders/Android%20One%20Perf)
+ * [Android Go](https://ci.chromium.org/buildbot/chromium.perf/android-go-perf/)
 
 ## Mac