TST: Use stable Python 3.10
TST: Use stable Python 3.10

Co-authored-by: Simon Conseil <1a73af9e7ae00182733b2292511b814be66f065f@saimon.org>
mhvk/astropy,astropy/astropy,saimn/astropy,saimn/astropy,astropy/astropy,larrybradley/astropy,saimn/astropy,mhvk/astropy,StuartLittlefair/astropy,astropy/astropy,lpsinger/astropy,pllim/astropy,pllim/astropy,astropy/astropy,lpsinger/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,lpsinger/astropy,mhvk/astropy,StuartLittlefair/astropy,saimn/astropy,mhvk/astropy,pllim/astropy,StuartLittlefair/astropy,larrybradley/astropy,saimn/astropy,astropy/astropy,mhvk/astropy,larrybradley/astropy,lpsinger/astropy,larrybradley/astropy,pllim/astropy,larrybradley/astropy,pllim/astropy,lpsinger/astropy