TST: Pin numpy<1.18 for Windows
TST: Pin numpy<1.18 for Windows

saimn/astropy,dhomeier/astropy,astropy/astropy,pllim/astropy,dhomeier/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,StuartLittlefair/astropy,pllim/astropy,lpsinger/astropy,lpsinger/astropy,mhvk/astropy,lpsinger/astropy,larrybradley/astropy,pllim/astropy,StuartLittlefair/astropy,larrybradley/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,astropy/astropy,saimn/astropy,larrybradley/astropy,mhvk/astropy,lpsinger/astropy,pllim/astropy,StuartLittlefair/astropy,pllim/astropy,astropy/astropy,mhvk/astropy,astropy/astropy,saimn/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,saimn/astropy,mhvk/astropy,saimn/astropy,StuartLittlefair/astropy,astropy/astropy,dhomeier/astropy