Remove google analytics, as per ASF Privacy Policy.

[rbowen]

This PR removes Google Analytics from the docs site template. This is in order to bring the site into compliance with ASF privacy policy - https://privacy.apache.org/policies/website-policy.html

Note that if you still want/need analytics, you can use Matamo - details at https://privacy.apache.org/matomo/

[brahmareddybattula]

@rbowen thanks for reporting this and providing the info. Can we raise jira for this and update the commit message.?

[JiaLiangC]

+1