Removed postman playground from docs
Removed postman playground from docs

Change-Id: I05ab5cafad68b9da8bd7b551384a0031e736c5d1

rafinskipg/corbel-composr,corbel-platform/corbel-composr,jscMR/corbel-composr,jarpi/corbel-composr,milingo/corbel-composr,bq/corbel-composer