Revert back to using the default r8 jar for buildtools

We have never actually updated the buildtools version independently of
the normal updates (except updating it to be the same)

If we ever need to update it to a seperate version, that is is easily
accomplished by changing the path.

Bug: b/134507641
Test: m -j55 sdk and run d8 in the sdk zip validating the version
Change-Id: Ib1540b22921e10946ec33076f1db40c50bccac76
1 file changed