Update trybot documentation on -ForTest

The "Added Symbols named -ForTest" check is no longer disabled.

Change-Id: I3b42550f138de7146627591b5dc4b48d2406e2e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1937861
Auto-Submit: Natalie Chouinard <chouinard@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719389}

docs/speed/binary_size/android_binary_size_trybot.md

@@ -118,7 +118,6 @@ For more information on when to use `const char *` vs `const char[]`, see
 - **What:** This checks that we don't have symbols with “ForTest” in their name
   in an optimized release binary.
 - **Why:** To prevent shipping unused test-only code to end-users.
-- *This check is currently disabled (limit set to 100)*.
 
 #### What to do if the Check Fails?