Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/android/test_suites.go b/android/test_suites.go
index 55e1da7..b570b23 100644
--- a/android/test_suites.go
+++ b/android/test_suites.go
@@ -57,7 +57,7 @@
 
 func robolectricTestSuite(ctx SingletonContext, files map[string]InstallPaths) WritablePath {
 	var installedPaths InstallPaths
-	for _, module := range SortedStringKeys(files) {
+	for _, module := range SortedKeys(files) {
 		installedPaths = append(installedPaths, files[module]...)
 	}
 	testCasesDir := pathForInstall(ctx, ctx.Config().BuildOS, X86, "testcases", false)