Truncate SVR2 IDs to 16 bytes rather than 10.

service/src/main/java/org/whispersystems/textsecuregcm/controllers/SecureValueRecovery2Controller.java

@@ -29,6 +29,7 @@ public class SecureValueRecovery2Controller {
         .builder(cfg.userAuthenticationTokenSharedSecret())
         .withUserDerivationKey(cfg.userIdTokenSharedSecret())
         .prependUsername(false)
+        .withTruncateLength(16)
         .build();
   }