Bump AS to 0.31.2, which has the necessary API

Author: Grisha Kruglov

buildSrc/src/main/java/Dependencies.kt

@@ -25,7 +25,7 @@ object Versions {
     const val jna = "5.2.0"
     const val disklrucache = "2.0.2"
 
-    const val mozilla_appservices = "0.31.0"
+    const val mozilla_appservices = "0.31.2"
     const val servo = "0.0.1.20181017.aa95911"
 
     const val material = "1.0.0"