Update .gitignore to exclude the doc/src/i18n/ directory
Update .gitignore to exclude the doc/src/i18n/ directory

We recently added translations of our tutorial. These are kept in .po
files, but when generated is stored in the doc/src/i18n/. Have git
ignore it.

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