go/ast: fix typo in comment
go/ast: fix typo in comment

Change-Id: I719231466286b3c0135314388a7c560ef44d7c35
Reviewed-on: https://go-review.googlesource.com/20130
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

momchil-velikov/go,Samurais/go,cloudflare/go,goodlang/good,cloudflare/go,cloudflare/go,theif519/go,mwhudson/go,derekmarcotte/go,momchil-velikov/go,CAFxX/go,codestation/go,golang/go,nawawi/go,nawawi/go,CAFxX/go,4ad/go,vanloswang/go,binarycrusader/go,CAFxX/go,Cofyc/go,Cofyc/go,binarycrusader/go,codestation/go,codestation/go,goodlang/good,CAFxX/go,mwhudson/go,suncycheng/go,theif519/go,miolini/go,polyverse-security/go,codestation/go,derekmarcotte/go,CAFxX/go,miolini/go,Cofyc/go,derekmarcotte/go,linux-on-ibm-z/go,Cofyc/go,ImJasonH/go,polyverse-security/go,akutz/go,vsekhar/elastic-go,momchil-velikov/go,4ad/go,cloudflare/go,ImJasonH/go,nawawi/go,ganboing/go-esx,mwhudson/go,akutz/go,Samurais/go,cloudflare/go,derekmarcotte/go,miolini/go,theif519/go,vanloswang/go,mwhudson/go,josharian/go,suncycheng/go,miolini/go,akutz/go,linux-on-ibm-z/go,4ad/go,mwhudson/go,vsekhar/elastic-go,theif519/go,linux-on-ibm-z/go,theif519/go,polyverse-security/go,suncycheng/go,akutz/go,vanloswang/go,linux-on-ibm-z/go,Cofyc/go,vanloswang/go,CAFxX/go,ImJasonH/go,ganboing/go-esx,binarycrusader/go,Samurais/go,theif519/go,vanloswang/go,josharian/go,ImJasonH/go,binarycrusader/go,4ad/go,Cofyc/go,golang/go,mwhudson/go,polyverse-security/go,codestation/go,Cofyc/go,goodlang/good,suncycheng/go,vsekhar/elastic-go,binarycrusader/go,nawawi/go,4ad/go,momchil-velikov/go,Samurais/go,cloudflare/go,codestation/go,nawawi/go,polyverse-security/go,akutz/go,ganboing/go-esx,codestation/go,josharian/go,akutz/go,josharian/go,derekmarcotte/go,derekmarcotte/go,vanloswang/go,CAFxX/go,suncycheng/go,polyverse-security/go,cloudflare/go,ganboing/go-esx,ganboing/go-esx,golang/go,ImJasonH/go,vsekhar/elastic-go,nawawi/go,golang/go,goodlang/good,akutz/go,nawawi/go,momchil-velikov/go,mwhudson/go,miolini/go,momchil-velikov/go,vsekhar/elastic-go,derekmarcotte/go,ImJasonH/go,golang/go,binarycrusader/go,Samurais/go,linux-on-ibm-z/go,goodlang/good,cloudflare/go,goodlang/good,golang/go,suncycheng/go,golang/go,polyverse-security/go,theif519/go,vanloswang/go,mwhudson/go,CAFxX/go,suncycheng/go,Samurais/go,4ad/go,goodlang/good,vanloswang/go,josharian/go,josharian/go,miolini/go,ImJasonH/go,momchil-velikov/go,linux-on-ibm-z/go,4ad/go,binarycrusader/go,ganboing/go-esx,golang/go,christopher-henderson/Go,theif519/go,ganboing/go-esx,miolini/go,binarycrusader/go,codestation/go,linux-on-ibm-z/go,josharian/go,vsekhar/elastic-go,Samurais/go,miolini/go,akutz/go,Cofyc/go,momchil-velikov/go,nawawi/go,josharian/go,vsekhar/elastic-go,vsekhar/elastic-go,suncycheng/go,linux-on-ibm-z/go,ImJasonH/go,4ad/go,ganboing/go-esx,polyverse-security/go,Samurais/go,derekmarcotte/go,goodlang/good