Remove cache group "ext.vector" from modules definitions

This will save ~ 2 http requests on every page. Aside from the
original RL merge into core, I suspect this might be the biggest
request reducing commit to date (in ratio of http requests
reduced per number of lines changed in the commit).

Bug: 51564
Change-Id: I9889563a5ce847ce82a8cb417768addebad6f19e