test_external: Fix a test that checked availability of wrong backend
test_external: Fix a test that checked availability of wrong backend

atsao72/sympy,MechCoder/sympy,vipulroxx/sympy,garvitr/sympy,Shaswat27/sympy,abhiii5459/sympy,Arafatk/sympy,madan96/sympy,saurabhjn76/sympy,jaimahajan1997/sympy,Arafatk/sympy,MridulS/sympy,oliverlee/sympy,vipulroxx/sympy,rahuldan/sympy,jamesblunt/sympy,vipulroxx/sympy,kmacinnis/sympy,lindsayad/sympy,meghana1995/sympy,sampadsaha5/sympy,mcdaniel67/sympy,asm666/sympy,Titan-C/sympy,Designist/sympy,hargup/sympy,pernici/sympy,mcdaniel67/sympy,jamesblunt/sympy,Titan-C/sympy,pbrady/sympy,farhaanbukhsh/sympy,emon10005/sympy,iamutkarshtiwari/sympy,MridulS/sympy,debugger22/sympy,shipci/sympy,Designist/sympy,drufat/sympy,atsao72/sympy,iamutkarshtiwari/sympy,lidavidm/sympy,debugger22/sympy,Gadal/sympy,Arafatk/sympy,maniteja123/sympy,dqnykamp/sympy,AkademieOlympia/sympy,Davidjohnwilson/sympy,Davidjohnwilson/sympy,farhaanbukhsh/sympy,chaffra/sympy,postvakje/sympy,sunny94/temp,cccfran/sympy,AunShiLord/sympy,Sumith1896/sympy,Mitchkoens/sympy,yukoba/sympy,Curious72/sympy,asm666/sympy,kumarkrishna/sympy,shikil/sympy,debugger22/sympy,amitjamadagni/sympy,cccfran/sympy,Titan-C/sympy,AunShiLord/sympy,atreyv/sympy,AunShiLord/sympy,kevalds51/sympy,saurabhjn76/sympy,cswiercz/sympy,toolforger/sympy,skidzo/sympy,sunny94/temp,lidavidm/sympy,garvitr/sympy,Curious72/sympy,ChristinaZografou/sympy,drufat/sympy,pandeyadarsh/sympy,chaffra/sympy,Vishluck/sympy,abloomston/sympy,AkademieOlympia/sympy,moble/sympy,shikil/sympy,abloomston/sympy,pandeyadarsh/sympy,dqnykamp/sympy,Sumith1896/sympy,sampadsaha5/sympy,atreyv/sympy,wyom/sympy,mafiya69/sympy,Sumith1896/sympy,jerli/sympy,emon10005/sympy,hrashk/sympy,Gadal/sympy,lindsayad/sympy,moble/sympy,jbbskinny/sympy,Curious72/sympy,kaichogami/sympy,shipci/sympy,abhiii5459/sympy,diofant/diofant,sahmed95/sympy,cccfran/sympy,meghana1995/sympy,abhiii5459/sympy,Shaswat27/sympy,jaimahajan1997/sympy,sahilshekhawat/sympy,atsao72/sympy,rahuldan/sympy,beni55/sympy,ahhda/sympy,Vishluck/sympy,maniteja123/sympy,Mitchkoens/sympy,aktech/sympy,Vishluck/sympy,beni55/sympy,shikil/sympy,oliverlee/sympy,minrk/sympy,ga7g08/sympy,madan96/sympy,lindsayad/sympy,ahhda/sympy,yukoba/sympy,AkademieOlympia/sympy,maniteja123/sympy,jamesblunt/sympy,ahhda/sympy,cswiercz/sympy,hrashk/sympy,hrashk/sympy,liangjiaxing/sympy,yashsharan/sympy,wanglongqi/sympy,liangjiaxing/sympy,oliverlee/sympy,ChristinaZografou/sympy,grevutiu-gabriel/sympy,mafiya69/sympy,yashsharan/sympy,moble/sympy,wanglongqi/sympy,madan96/sympy,mafiya69/sympy,yashsharan/sympy,farhaanbukhsh/sympy,kaichogami/sympy,kumarkrishna/sympy,MridulS/sympy,asm666/sympy,toolforger/sympy,kmacinnis/sympy,iamutkarshtiwari/sympy,Mitchkoens/sympy,aktech/sympy,postvakje/sympy,VaibhavAgarwalVA/sympy,sahilshekhawat/sympy,Designist/sympy,sahilshekhawat/sympy,atreyv/sympy,lidavidm/sympy,aktech/sympy,cswiercz/sympy,abloomston/sympy,wyom/sympy,sahmed95/sympy,souravsingh/sympy,jbbskinny/sympy,amitjamadagni/sympy,kumarkrishna/sympy,garvitr/sympy,bukzor/sympy,skidzo/sympy,pandeyadarsh/sympy,kaichogami/sympy,kmacinnis/sympy,kaushik94/sympy,VaibhavAgarwalVA/sympy,skidzo/sympy,bukzor/sympy,toolforger/sympy,wanglongqi/sympy,MechCoder/sympy,pbrady/sympy,liangjiaxing/sympy,saurabhjn76/sympy,sampadsaha5/sympy,hargup/sympy,souravsingh/sympy,wyom/sympy,postvakje/sympy,skirpichev/omg,jerli/sympy,kevalds51/sympy,ga7g08/sympy,shipci/sympy,flacjacket/sympy,Gadal/sympy,jaimahajan1997/sympy,ChristinaZografou/sympy,pbrady/sympy,kevalds51/sympy,sunny94/temp,rahuldan/sympy,beni55/sympy,kaushik94/sympy,chaffra/sympy,grevutiu-gabriel/sympy,MechCoder/sympy,minrk/sympy,kaushik94/sympy,grevutiu-gabriel/sympy,srjoglekar246/sympy,jbbskinny/sympy,jerli/sympy,Shaswat27/sympy,souravsingh/sympy,ga7g08/sympy,bukzor/sympy,mcdaniel67/sympy,yukoba/sympy,Davidjohnwilson/sympy,emon10005/sympy,hargup/sympy,dqnykamp/sympy,drufat/sympy,meghana1995/sympy,sahmed95/sympy,VaibhavAgarwalVA/sympy