TST: clean deprecation warnings for xref #19980 (#20013)
TST: clean deprecation warnings for xref #19980 (#20013)

xfail some mpl > 2.1.2 tests
pandas-dev/pandas,rs2/pandas,rs2/pandas,gfyoung/pandas,cython-testbed/pandas,cython-testbed/pandas,toobaz/pandas,jreback/pandas,dsm054/pandas,kdebrab/pandas,jorisvandenbossche/pandas,louispotok/pandas,jorisvandenbossche/pandas,GuessWhoSamFoo/pandas,GuessWhoSamFoo/pandas,cython-testbed/pandas,louispotok/pandas,kdebrab/pandas,rs2/pandas,kdebrab/pandas,harisbal/pandas,jreback/pandas,pratapvardhan/pandas,dsm054/pandas,dsm054/pandas,pandas-dev/pandas,harisbal/pandas,datapythonista/pandas,jreback/pandas,gfyoung/pandas,pratapvardhan/pandas,louispotok/pandas,jorisvandenbossche/pandas,jorisvandenbossche/pandas,jreback/pandas,harisbal/pandas,pandas-dev/pandas,cbertinato/pandas,MJuddBooth/pandas,dsm054/pandas,MJuddBooth/pandas,toobaz/pandas,louispotok/pandas,pratapvardhan/pandas,MJuddBooth/pandas,cbertinato/pandas,TomAugspurger/pandas,TomAugspurger/pandas,GuessWhoSamFoo/pandas,toobaz/pandas,cython-testbed/pandas,pratapvardhan/pandas,cython-testbed/pandas,kdebrab/pandas,gfyoung/pandas,pratapvardhan/pandas,datapythonista/pandas,amolkahat/pandas,TomAugspurger/pandas,MJuddBooth/pandas,kdebrab/pandas,amolkahat/pandas,pandas-dev/pandas,harisbal/pandas,amolkahat/pandas,amolkahat/pandas,cbertinato/pandas,datapythonista/pandas,MJuddBooth/pandas,rs2/pandas,harisbal/pandas,amolkahat/pandas,TomAugspurger/pandas,datapythonista/pandas,dsm054/pandas,louispotok/pandas,cbertinato/pandas,cbertinato/pandas,gfyoung/pandas,GuessWhoSamFoo/pandas,gfyoung/pandas,toobaz/pandas,toobaz/pandas,jreback/pandas,GuessWhoSamFoo/pandas