Revert "Boxplot should not require a datetime column (#5096)" (#7655)
Revert "Boxplot should not require a datetime column (#5096)" (#7655)

This reverts commit 1ae000a26220c024f3f904d9049cfcd4b1e461e7.
airbnb/caravel,zhouyao1994/incubator-superset,mistercrunch/panoramix,airbnb/superset,airbnb/superset,airbnb/caravel,apache/incubator-superset,apache/incubator-superset,airbnb/superset,apache/incubator-superset,airbnb/superset,mistercrunch/panoramix,zhouyao1994/incubator-superset,airbnb/caravel,airbnb/caravel,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,apache/incubator-superset,mistercrunch/panoramix,zhouyao1994/incubator-superset,mistercrunch/panoramix,apache/incubator-superset