(Reuters) - Experian Plc, the world's biggest credit data firm, said on Wednesday that it had agreed with rival ClearScore to abandon their proposed merger, after Britain's competition watchdog indicated in November that it may block the deal."Taking into account subsequent interaction with the CMA (Competition and Markets Authority), Experian does not believe that the CMA will approve the proposed acquisition of ClearScore on satisfactory terms," Experian said in a statement.The CMA had warned..