Remove library decorator for extracting headers

It is unused and removing it allows us to use the same function for
prebuilt/not libraries.

Test: bp2build.sh
Change-Id: I92ac56496cff2c2e55d6eb9f261fe75a1b232856
diff --git a/cc/prebuilt.go b/cc/prebuilt.go
index f54c6f8..57f7299 100644
--- a/cc/prebuilt.go
+++ b/cc/prebuilt.go
@@ -354,7 +354,7 @@
 
 func prebuiltLibraryStaticBp2Build(ctx android.TopDownMutatorContext, module *Module, fullBuild bool) {
 	prebuiltAttrs := Bp2BuildParsePrebuiltLibraryProps(ctx, module, true)
-	exportedIncludes := Bp2BuildParseExportedIncludesForPrebuiltLibrary(ctx, module)
+	exportedIncludes := bp2BuildParseExportedIncludes(ctx, module, nil)
 
 	attrs := &bazelPrebuiltLibraryStaticAttributes{
 		Static_library:         prebuiltAttrs.Src,