Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/cc/stub_library.go b/cc/stub_library.go
index 76da782..f324dcc 100644
--- a/cc/stub_library.go
+++ b/cc/stub_library.go
@@ -73,7 +73,7 @@
 
 func (s *stubLibraries) MakeVars(ctx android.MakeVarsContext) {
 	// Convert stub library file names into Makefile variable.
-	ctx.Strict("STUB_LIBRARIES", strings.Join(android.SortedStringKeys(s.stubLibraryMap), " "))
+	ctx.Strict("STUB_LIBRARIES", strings.Join(android.SortedKeys(s.stubLibraryMap), " "))
 
 	// Export the list of API XML files to Make.
 	sort.Strings(s.apiListCoverageXmlPaths)