React-docs Table Headers Disappear on Mobile

[redallen]

Table headers for props and css variables disappear on mobile view after #1656 (example).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[dgutride]

Can't repro (and react-docs are low priority since we'd like to replace gatsby and components with the config out of -org