Update session_api.rst
Update session_api.rst

fix grammar
gatling/gatling,timve/gatling,MykolaB/gatling,wiacekm/gatling,MykolaB/gatling,MykolaB/gatling,pwielgolaski/gatling,wiacekm/gatling,wiacekm/gatling,gatling/gatling,wiacekm/gatling,timve/gatling,MykolaB/gatling,gatling/gatling,pwielgolaski/gatling,gatling/gatling,timve/gatling,pwielgolaski/gatling,timve/gatling,gatling/gatling,pwielgolaski/gatling,wiacekm/gatling