TST: don't assert that matplotlib rejects shorthand hex colors (#33262)
TST: don't assert that matplotlib rejects shorthand hex colors (#33262)

From 3.2 it accepts them:
https://matplotlib.org/users/prev_whats_new/whats_new_3.2.0.html#digit-and-4-digit-hex-colors
jorisvandenbossche/pandas,jreback/pandas,gfyoung/pandas,jreback/pandas,dsm054/pandas,rs2/pandas,pandas-dev/pandas,TomAugspurger/pandas,TomAugspurger/pandas,jorisvandenbossche/pandas,pandas-dev/pandas,gfyoung/pandas,pandas-dev/pandas,jreback/pandas,gfyoung/pandas,jorisvandenbossche/pandas,rs2/pandas,datapythonista/pandas,datapythonista/pandas,dsm054/pandas,rs2/pandas,dsm054/pandas,TomAugspurger/pandas,datapythonista/pandas,datapythonista/pandas,rs2/pandas,dsm054/pandas,jreback/pandas,pandas-dev/pandas,dsm054/pandas,jreback/pandas,TomAugspurger/pandas,jorisvandenbossche/pandas,gfyoung/pandas,gfyoung/pandas