Codec2Client: remove vendor_available and apex_available

remove vendor_available and apex_available from
libcodec2_client_headers. The library is not needed to be linked from
h/w codec and/or s/w codec.

Bug: 251850069
Test: m
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:8769fa87b8676e7b4159887e780866c9f5170e63)
Change-Id: I3ed7fa1d7f025b1fb334659775eaab6add0c7747