Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/cc/util.go b/cc/util.go
index 4e10037..aa0f6b5 100644
--- a/cc/util.go
+++ b/cc/util.go
@@ -118,7 +118,7 @@
 // ...
 func installMapListFileRule(ctx android.SingletonContext, m map[string]string, path string) android.OutputPath {
 	var txtBuilder strings.Builder
-	for idx, k := range android.SortedStringKeys(m) {
+	for idx, k := range android.SortedKeys(m) {
 		if idx > 0 {
 			txtBuilder.WriteString("\n")
 		}