Remove java_api_contribution modules from .bp files

java_api_contribution modules are dynamically generated from droidstubs
modules or java_sdk_library_import, and is not a user-facing module.
Defining this module is a .bp file is a no-op.

Test: m nothing
Bug: 322242515
Change-Id: Id02754c66c7fc1fad9880187298694f4941f14e1
Flag: Exempt, Build files only