Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/bp2build/build_conversion.go b/bp2build/build_conversion.go
index 6c6631a..ced779c 100644
--- a/bp2build/build_conversion.go
+++ b/bp2build/build_conversion.go
@@ -227,7 +227,7 @@
 // the generated attributes are sorted to ensure determinism.
 func propsToAttributes(props map[string]string) string {
 	var attributes string
-	for _, propName := range android.SortedStringKeys(props) {
+	for _, propName := range android.SortedKeys(props) {
 		attributes += fmt.Sprintf("    %s = %s,\n", propName, props[propName])
 	}
 	return attributes