go-tour: don't use a pointer to a map in web crawl exercise It's unnecessary and misleading. Fixes #6322.
go-tour: don't use a pointer to a map in web crawl exercise
It's unnecessary and misleading.
Fixes #6322.

R=adg, dsymonds
CC=golang-dev
https://golang.org/cl/13361050

bbandaru/tour,shuLhan/tour,scryner/tour,zorion/go-tour-ca,Jasperste/tour,tamnd/tour,campoy/go-tour-ua,Jasperste/tour,LaPingvino/go-tour-nl,LaPingvino/go-tour-nl,shuLhan/go-tour-id,campoy/go-tour-ua,Go-zh/tour,Go-zh/tour,phoorichet/tour,phoorichet/tour,golians/tour,zorion/go-tour-ca,scryner/tour,rofrol/go-tour-pl,golang/tour,tamnd/tour,LaPingvino/go-tour-eo,golians/tour,LaPingvino/go-tour-eo,rofrol/go-tour-pl,scryner/tour,Go-zh/tour,Jasperste/tour,LaPingvino/go-tour-eo,raindev/tour,ybin/tour,LaPingvino/go-tour-nl,bbandaru/tour,shuLhan/tour,rofrol/go-tour-pl,phoorichet/tour,ybin/tour,shuLhan/go-tour-id,scryner/tour,dupoxy/go-tour-fr,Go-zh/tour,bbandaru/tour,raindev/tour,tamnd/tour,ybin/tour,shuLhan/tour,shuLhan/go-tour-id,raindev/tour,dupoxy/go-tour-fr,dupoxy/go-tour-fr,golians/tour,campoy/go-tour-ua