Update api_levels.go instead of api_constants.bzl

This is a revert of aosp/2573034, but as a separate cl because the
filename has been changed. We're reverting aosp/2573034 because the
bazel migration has been cancelled and that api_constants.bzl file
was changed to not be used.

Ignore-AOSP-First: Someone else renamed this file in internal-only.

Bug: 315353489
Test: Manually ran this snippet of shell script
Change-Id: I3a51be1119109d2a6cf3959bdc8a48192872580f