polygerrit: Add note in README about running tests in Safari
polygerrit: Add note in README about running tests in Safari

Change-Id: Ie2da0221f2779a5d035e4062129ae696d254344f

GerritCodeReview/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,WANdisco/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,gerrit-review/gerrit,gerrit-review/gerrit