PERF: numexpr doesn't support floordiv, so don't try
Re-take of https://github.com/pandas-dev/pandas/pull/40727, see that PR for explanation.

Tests will still be failing (so don't merge yet ;)), but depend on #41161 to be fixed
so don't put the milestone as an indicator of not merge yet I made it draft to be clear  This is now passing, and the actual change was already reviewed / approved in #40727