pgo: remove speedometer2 from pgo generation

Speedometer3 is now the default, so no need to run speedometer2
anymore.

Bug: 331316078
Change-Id: I162be5779221be180f070e3bd58a22a5f8e1ea60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5403086


Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279875}