Use value that looks more like actual Personalization metadata.

Author: vic-flair

firebase-config/src/test/java/com/google/firebase/remoteconfig/internal/ConfigStorageClientTest.java

@@ -91,7 +91,7 @@ public void read_validContainerWithPersonalization_returnsContainer() throws Exc
         ConfigContainer.newBuilder(configContainer)
             .withPersonalizationMetadata(
                 new JSONObject(
-                    ImmutableMap.of(Personalization.EXTERNAL_ARM_VALUE_PARAM, "arm_value")))
+                    "{key1: {personalizationId: 'id1'}, key2: {personalizationId: 'id2'}}"))
             .build();
     storageClient.write(configWithPersonalization);
     Preconditions.checkArgument(getFileAsString().equals(configWithPersonalization.toString()));