Bug#1043240: transition: pandas 1.5 -> 2.1

[Rebecca N. Palmer]

Control: retitle -1 transition: pandas 1.5 -> 2.1

pandas 2.1 is now in experimental.  In addition to the above, it breaks 
these packages:
astropy dask patsy pymatgen python-cooler python-geopandas q2-demux 
q2-taxa q2-types seaborn tqdm
and maybe python-hypothesis.

(python-pauvre and sunpy are probably already fixed; drms and skyfield 
are probably unrelated to pandas.)

Build logs:
https://launchpad.net/~rebecca-palmer/+archive/ubuntu/pandas2p1/+builds?build_text=&build_state=failed

Autopkgtest logs:
https://qa.debian.org/excuses.php?experimental=1&package=pandas