Replace gson star import with explicit imports in ObjectJsonSerializer

Fixes checkstyle AvoidStarImport violation on com.google.gson.*.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: sacOO7

lib/src/main/java/io/ably/lib/object/serialization/ObjectJsonSerializer.java

@@ -1,6 +1,12 @@
 package io.ably.lib.object.serialization;
 
-import com.google.gson.*;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
 import io.ably.lib.util.Log;
 
 import java.lang.reflect.Type;