docs: remove references to superset-ui-plugins (#9639)
docs: remove references to superset-ui-plugins (#9639)

`superset-ui-plugins` has been deprecated.[1] We now manages
all basic visualizations in apache-superset/superset-ui .

[1] https://github.com/apache-superset/superset-ui/pull/332
airbnb/caravel,mistercrunch/panoramix,airbnb/caravel,airbnb/caravel,airbnb/caravel,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,airbnb/superset,apache/incubator-superset,airbnb/superset,apache/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/superset,mistercrunch/panoramix,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix