Android: Fix rebuild_baselines.py for upstream

Previously, upstream baselines did not set
enable_chrome_android_internal=false, which caused the baselines
generated by the script to differ from what upstream bots expected.

Now the script can be run without any arguments and will update both
upstream and downstream correctly (if //clank exists).

Bug: 1378684
Change-Id: I2b9ea3378c8c6d26eff560a1dccd12c650645fd4
Fixed: 1378684
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3982940
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Auto-Submit: Peter Wen <wnwen@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1063994}