Use android-* targets instead of torbrowser-android-* targets in projects/tor-onion-proxy-library/config

In projects/tor-onion-proxy-library/config we build snowflake and obfs4 with target_prepend and the torbrowser-android-* targets. The torbrowser-android-* targets are expanded to the corresponding android-* target and the android target. However I think the android target is already in the list of current targets when we build the tor-onion-proxy-library projet. So we could use the android-* targets to avoid including the android target twice.