docs: add Symmetrics to users list (#17028)
docs: add Symmetrics to users list (#17028)

* Add Symmetrics 

Symmetrics provides intelligent metrics to help make connections and matches among job seekers, recruiters, staffers and employers

* Remove trailing space after heading
airbnb/caravel,airbnb/caravel,zhouyao1994/incubator-superset,apache/incubator-superset,apache/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel