Replace SortedStringKeys with SortedKeys

Now that we have generics.

Bug: 193460475
Test: presubmits
Change-Id: I1594fd8feb505175d5c09c03ef397e5ffd5b09cb
diff --git a/apex/builder.go b/apex/builder.go
index a62f63c..7248d97 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -543,7 +543,7 @@
 
 	if len(installMapSet) > 0 {
 		var installs []string
-		installs = append(installs, android.SortedStringKeys(installMapSet)...)
+		installs = append(installs, android.SortedKeys(installMapSet)...)
 		a.SetLicenseInstallMap(installs)
 	}