Remove reference to j/c/g/c/b/Objects.toStringHelper.

Moving to MoreObjects is a bit interesting because the client library does not
yet depend on Guava 18 and Guava 18 doesn't support JDK5. However, the client
libraries already have a proxy class for Objects.toStringHelper so I just use
it instead.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=107617466

Author: ejona86

google-http-client/src/test/java/com/google/api/client/http/UrlEncodedParserTest.java

@@ -17,8 +17,8 @@
 import com.google.api.client.util.ArrayMap;
 import com.google.api.client.util.GenericData;
 import com.google.api.client.util.Key;
+import com.google.api.client.util.Objects;
 import com.google.api.client.util.Value;
-import com.google.common.base.Objects;
 
 import junit.framework.TestCase;