Pin jarjar'ed target telephony-protos to java_version 1.8.

This allows the default target java_version to advance before /
independently of jarjar support for higher (v53) class file
versions.

Bug: 72703434
Test: EXPERIMENTAL_USE_OPENJDK9=true USE_R8=true make checkbuild docs
      (in a client where CL http://r.android.com/596874 was reverted)

Change-Id: I10c56ddc6f84691045d2e6e494a26e7c797ba22a