Remove the presubmit progressive roll-out logic in `regen-test-files`.

ART run-tests (that are supported at build- and run-time) have been
used in `presubmit` and `mainline-presubmit` test groups in
`TEST_MAPPING` respectively since March 2021
(https://android-review.googlesource.com/c/platform/art/+/1619103) and
May 2021
(https://android-review.googlesource.com/c/platform/art/+/1714240).
As these tests have been reasonably stable since, remove the
progressive roll-out logic (used to promote run-tests from postsubmits
to presubmits) from script `test/utils/regen-test-files`.

Test: Run `art/test/utils/regen-test-files` and check there is no
      difference in generated files
Bug: 152374989
Bug: 169310621
Bug: 178703264
Change-Id: I8676bbe5e12bdc81feaff712a42d22e848293833
1 file changed