Fix last-released check of removed.txt

The last-released checks should check compatibility of the removed.txt
file generated from src with the checked in last-released removed.txt.
It was previously checking compatibility with the checked in removed.txt
at HEAD, which is what check_api is for.

Bug: 155197156
Test: m checkapi
Change-Id: I0f4eca5a30ee13e2c098ccf50e1b992adf4e22cb