Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/android/packaging.go b/android/packaging.go
index ecd84a2..4a9b591 100644
--- a/android/packaging.go
+++ b/android/packaging.go
@@ -240,7 +240,7 @@
 // entries into the specified directory.
 func (p *PackagingBase) CopySpecsToDir(ctx ModuleContext, builder *RuleBuilder, specs map[string]PackagingSpec, dir ModuleOutPath) (entries []string) {
 	seenDir := make(map[string]bool)
-	for _, k := range SortedStringKeys(specs) {
+	for _, k := range SortedKeys(specs) {
 		ps := specs[k]
 		destPath := dir.Join(ctx, ps.relPathInPackage).String()
 		destDir := filepath.Dir(destPath)