Rebase git command had a typo.
Rebase git command had a typo.

Edits to rebase instructions.

[skip ci]

StuartLittlefair/astropy,AustereCuriosity/astropy,larrybradley/astropy,DougBurke/astropy,aleksandr-bakanov/astropy,tbabej/astropy,funbaker/astropy,kelle/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,StuartLittlefair/astropy,saimn/astropy,dhomeier/astropy,astropy/astropy,AustereCuriosity/astropy,bsipocz/astropy,kelle/astropy,stargaser/astropy,joergdietrich/astropy,mhvk/astropy,funbaker/astropy,bsipocz/astropy,tbabej/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,bsipocz/astropy,lpsinger/astropy,lpsinger/astropy,saimn/astropy,pllim/astropy,stargaser/astropy,funbaker/astropy,stargaser/astropy,stargaser/astropy,saimn/astropy,lpsinger/astropy,kelle/astropy,DougBurke/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,astropy/astropy,saimn/astropy,MSeifert04/astropy,StuartLittlefair/astropy,funbaker/astropy,pllim/astropy,dhomeier/astropy,saimn/astropy,AustereCuriosity/astropy,joergdietrich/astropy,tbabej/astropy,pllim/astropy,tbabej/astropy,MSeifert04/astropy,larrybradley/astropy,bsipocz/astropy,astropy/astropy,aleksandr-bakanov/astropy,astropy/astropy,joergdietrich/astropy,pllim/astropy,dhomeier/astropy,pllim/astropy,lpsinger/astropy,larrybradley/astropy,tbabej/astropy,mhvk/astropy,StuartLittlefair/astropy,lpsinger/astropy,joergdietrich/astropy,dhomeier/astropy,dhomeier/astropy,mhvk/astropy,kelle/astropy,joergdietrich/astropy,kelle/astropy,MSeifert04/astropy,DougBurke/astropy,larrybradley/astropy,DougBurke/astropy,larrybradley/astropy,MSeifert04/astropy