doc: fix typo "heirarchy"
doc: fix typo "heirarchy"

Change-Id: Iae2bf44ec15975f440d026fd52fcccfbd9c598d9
Reviewed-on: https://go-review.googlesource.com/17740
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/go,deft-code/go,4ad/go,mwhudson/go,deft-code/go,roth1002/go,goodlang/good,linux-on-ibm-z/go,CAFxX/go,Cofyc/go,vsekhar/elastic-go,sndnvaps/go,kim-racktop/go,nawawi/go,kim-racktop/go,4ad/go,vsekhar/elastic-go,theif519/go,goodlang/good,vanloswang/go,kim-racktop/go,roth1002/go,binarycrusader/go,theif519/go,josharian/go,codestation/go,momchil-velikov/go,Samurais/go,deft-code/go,derekmarcotte/go,Cofyc/go,Cofyc/go,christopher-henderson/Go,CAFxX/go,Samurais/go,golang/go,cyberroadie/go,cyberroadie/go,goodlang/good,vsekhar/elastic-go,ImJasonH/go,derekmarcotte/go,polyverse-security/go,suncycheng/go,momchil-velikov/go,sndnvaps/go,akutz/go,mwhudson/go,ganboing/go-esx,4ad/go,Endika/go,ImJasonH/go,linux-on-ibm-z/go,ImJasonH/go,vsekhar/elastic-go,polyverse-security/go,kim-racktop/go,suncycheng/go,ganboing/go-esx,cyberroadie/go,binarycrusader/go,Samurais/go,momchil-velikov/go,mwhudson/go,momchil-velikov/go,josharian/go,binarycrusader/go,miolini/go,ImJasonH/go,linux-on-ibm-z/go,Samurais/go,roth1002/go,ganboing/go-esx,goodlang/good,codestation/go,derekmarcotte/go,Endika/go,golang/go,sndnvaps/go,Endika/go,binarycrusader/go,binarycrusader/go,theif519/go,CAFxX/go,ganboing/go-esx,sndnvaps/go,goodlang/good,golang/go,4ad/go,nawawi/go,mwhudson/go,kim-racktop/go,Cofyc/go,cloudflare/go,vanloswang/go,ImJasonH/go,suncycheng/go,kim-racktop/go,josharian/go,suncycheng/go,Endika/go,vsekhar/elastic-go,nawawi/go,Samurais/go,sndnvaps/go,Cofyc/go,miolini/go,CAFxX/go,nawawi/go,goodlang/good,suncycheng/go,golang/go,cyberroadie/go,codestation/go,polyverse-security/go,cloudflare/go,CAFxX/go,4ad/go,cyberroadie/go,4ad/go,akutz/go,mwhudson/go,kim-racktop/go,codestation/go,vsekhar/elastic-go,nawawi/go,nawawi/go,CAFxX/go,binarycrusader/go,codestation/go,linux-on-ibm-z/go,cloudflare/go,polyverse-security/go,josharian/go,roth1002/go,josharian/go,vanloswang/go,ganboing/go-esx,binarycrusader/go,Samurais/go,theif519/go,suncycheng/go,cyberroadie/go,polyverse-security/go,sndnvaps/go,theif519/go,josharian/go,Cofyc/go,cloudflare/go,CAFxX/go,linux-on-ibm-z/go,cloudflare/go,polyverse-security/go,roth1002/go,cyberroadie/go,miolini/go,binarycrusader/go,ImJasonH/go,Endika/go,miolini/go,sndnvaps/go,linux-on-ibm-z/go,vanloswang/go,nawawi/go,akutz/go,vsekhar/elastic-go,derekmarcotte/go,cyberroadie/go,mwhudson/go,cloudflare/go,Samurais/go,Endika/go,codestation/go,cloudflare/go,CAFxX/go,goodlang/good,golang/go,linux-on-ibm-z/go,sndnvaps/go,deft-code/go,vanloswang/go,golang/go,momchil-velikov/go,vanloswang/go,josharian/go,ImJasonH/go,ganboing/go-esx,miolini/go,4ad/go,vanloswang/go,Cofyc/go,momchil-velikov/go,akutz/go,theif519/go,derekmarcotte/go,polyverse-security/go,theif519/go,codestation/go,akutz/go,ganboing/go-esx,momchil-velikov/go,akutz/go,goodlang/good,derekmarcotte/go,derekmarcotte/go,suncycheng/go,roth1002/go,mwhudson/go,ImJasonH/go,Cofyc/go,derekmarcotte/go,golang/go,suncycheng/go,josharian/go,mwhudson/go,theif519/go,akutz/go,ganboing/go-esx,miolini/go,linux-on-ibm-z/go,miolini/go,akutz/go,deft-code/go,kim-racktop/go,deft-code/go,momchil-velikov/go,vsekhar/elastic-go,Endika/go,codestation/go,polyverse-security/go,vanloswang/go,cloudflare/go,roth1002/go,deft-code/go,Samurais/go,deft-code/go,4ad/go,nawawi/go,roth1002/go,Endika/go,miolini/go