Fix typo in .travis.yml
Fix typo in .travis.yml

kaichogami/sympy,ChristinaZografou/sympy,rahuldan/sympy,lindsayad/sympy,Curious72/sympy,yashsharan/sympy,mafiya69/sympy,madan96/sympy,chaffra/sympy,drufat/sympy,yashsharan/sympy,postvakje/sympy,Curious72/sympy,postvakje/sympy,skidzo/sympy,lindsayad/sympy,aktech/sympy,aktech/sympy,skidzo/sympy,sampadsaha5/sympy,kaichogami/sympy,kaushik94/sympy,madan96/sympy,kaichogami/sympy,jaimahajan1997/sympy,rahuldan/sympy,rahuldan/sympy,sampadsaha5/sympy,yashsharan/sympy,mafiya69/sympy,jaimahajan1997/sympy,kaushik94/sympy,kaushik94/sympy,Titan-C/sympy,chaffra/sympy,drufat/sympy,jerli/sympy,skidzo/sympy,ChristinaZografou/sympy,aktech/sympy,mafiya69/sympy,jerli/sympy,hargup/sympy,jaimahajan1997/sympy,postvakje/sympy,Titan-C/sympy,hargup/sympy,hargup/sympy,Titan-C/sympy,lindsayad/sympy,souravsingh/sympy,souravsingh/sympy,jerli/sympy,sampadsaha5/sympy,Curious72/sympy,souravsingh/sympy,ChristinaZografou/sympy,madan96/sympy,drufat/sympy,chaffra/sympy