Fix typo in example in association_basics.rdoc
Fix typo in example in association_basics.rdoc

freshpay/sequel,beni55/sequel,freshpay/sequel,gferguson-gd/sequel,knut2/sequel,offshore-safety/sequel,nju520/sequel,t-morgan/sequel,offshore-safety/sequel,pfarrell/sequel,bigfix/sequel,seeARMS/sequel,uhoh-itsmaciek/sequel,knut2/sequel,nicohvi/sequel,pfarrell/sequel,dennis-d/custom_sequel,gferguson-gd/sequel,t-morgan/sequel,yazshel/sequel,offshore-safety/sequel,davidbegin/sequel,chef/sequel,seeARMS/sequel,Marketcircle/sequel,nju520/sequel,yazshel/sequel,davidbegin/sequel,nicohvi/sequel,mpalmer/sequel,reubano/sequel,reubano/sequel,dennis-d/custom_sequel,beni55/sequel,mpalmer/sequel,uhoh-itsmaciek/sequel