Remove gender micro-survey from VisualEditor

The 'ext.visualEditor.genderSurvey' module was introduced in I2b4aba6a9
for the purpose of instrumenting a short-lived microsurvey that would be
concomitant with the deployment of VisualEditor. The survey has now run
its course; this patch removes its code.

Change-Id: I8be6198a66957d792757a5312e9e71b3c8cdd1e3
Merge "Remove gender micro-survey from VisualEditor"