Revert "Add scripts to generate java APIs used by Mainline modules."

This reverts commit c92380f001.

Reason for revert:
DroidMonitor:

DroidMonitor-triggered revert due to breakage
https://android-build.googleplex.com/builds/quarterdeck?branch=git_master&target=mainline_modules_arm64-userdebug&lkgb=7898389&lkbb=7900541&fkbb=7898474,
bug 205746850

Change-Id: Ibd84dfe68dfe150b7e05b4287364d1946375bf72

apex/testing.go

@@ -24,7 +24,6 @@ var PrepareForTestWithApexBuildComponents = android.GroupFixturePreparers(
 	android.MockFS{
 		// Needed by apex.
 		"system/core/rootdir/etc/public.libraries.android.txt": nil,
-		"build/soong/scripts/gen_java_usedby_apex.sh":          nil,
 		"build/soong/scripts/gen_ndk_backedby_apex.sh":         nil,
 		// Needed by prebuilt_apex.
 		"build/soong/scripts/unpack-prebuilt-apex.sh": nil,