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/bp2build/conversion.go b/bp2build/conversion.go
index d98b6a3..6fb2823 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -96,17 +96,9 @@
 # This file was automatically generated by bp2build for the Bazel migration project.
 # Feel free to edit or test it, but do *not* check it into your version control system.
 `
-			if targets.hasHandcraftedTargets() {
-				// For BUILD files with both handcrafted and generated targets,
-				// don't hardcode actual content, like package() declarations.
-				// Leave that responsibility to the checked-in BUILD file
-				// instead.
-				content += `# This file contains generated targets and handcrafted targets that are manually managed in the source tree.`
-			} else {
-				// For fully-generated BUILD files, hardcode the default visibility.
-				content += "package(default_visibility = [\"//visibility:public\"])"
-			}
-			content += "\n"
+
+			// Hardcode the default visibility.
+			content += "package(default_visibility = [\"//visibility:public\"])\n"
 			content += targets.LoadStatements()
 		} else if mode == QueryView {
 			content = soongModuleLoad