Remove old BUILD file merging code

It's not needed anymore since aosp/2197837,
it should've been removed in that cl but I forgot.

Bug: 234167862
Test: ./build/bazel/ci/bp2build.sh
Change-Id: I3d67a6e1894ad401525070ad37d3158708898306
diff --git a/android/allowlists/allowlists.go b/android/allowlists/allowlists.go
index 0cdf792..3223b04 100644
--- a/android/allowlists/allowlists.go
+++ b/android/allowlists/allowlists.go
@@ -295,6 +295,7 @@
 		"external/bazel-skylib":/* recursive = */ true,
 		"external/guava":/* recursive = */ true,
 		"external/jsr305":/* recursive = */ true,
+		"external/protobuf":/* recursive = */ false,
 		"frameworks/ex/common":/* recursive = */ true,
 
 		"packages/apps/Music":/* recursive = */ true,
@@ -302,6 +303,7 @@
 
 		"prebuilts/bazel":/* recursive = */ true,
 		"prebuilts/bundletool":/* recursive = */ true,
+		"prebuilts/clang/host/linux-x86":/* recursive = */ false,
 		"prebuilts/gcc":/* recursive = */ true,
 		"prebuilts/build-tools":/* recursive = */ true,
 		"prebuilts/jdk/jdk11":/* recursive = */ false,