Remove annotation_processors property

Now that there are no uses left of annotation_processors remove
the property.

If there are no annotation processor classes for javac for a module,
due to an empty "plugins" property or using kapt for annotation
processors, pass -proc:none to javac to ensure it does not try
to run any annotation processors found in the classpath.

Bug: 77284273
Test: plugin_test.go, kotlin_test.go
Change-Id: I3823d9fec8d3d07d2e49b1d97839f7fcbdd35647