Bug#931557: transition: pandas 0.23 -> 0.25

[Rebecca N. Palmer]

Control: retitle -1 transition: pandas 0.23 -> 0.25

I now have pandas 0.25.2 in experimental, with these autopkgtest failures:
pandas itself: probably I forgot to add a dependency (it passed locally, 
but in the same chroot as the build)
statsmodels: looks like a reappearance of #923707 and some 
fail-on-(deprecation)-warnings.  Will probably upgrade this to 0.10.
cnvkit,python-skbio,q2-types,snakemake: Not investigated.

https://release.debian.org/britney/pseudo-excuses-experimental.html