Fixed typo in mechanics docs
Fixed typo in mechanics docs

An example had a typo, but didn't have a complete test because it took so long,
so it never came up.

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