Change libbt-platform-protos dependency

Move the dependency to use the target included in
//external/proto_logging instead. This will be provided via cros_workon
for ChromeOS and in the prepared platform-dir for Linux build.

Bug: 176847256
Tag: #floss
Test: atest --host bluetooth_test_gd
Change-Id: I86da8ca8e7b666ccdc4cc36680f90083bbe76dfb