fix comment bug in make build-docs (#7420)

Makefile

@@ -199,6 +199,9 @@ godocs:
 	@echo "--> Wait a few seconds and visit http://localhost:6060/pkg/github.com/cosmos/cosmos-sdk/types"
 	godoc -http=:6060
 
+# This builds a docs site for each branch/tag in `./docs/versions`
+# and copies each site to a version prefixed path. The last entry inside
+# the `versions` file will be the default root index.html.
 build-docs:
 	@cd docs && \
 	while read -a p; do \
@@ -207,7 +210,6 @@ build-docs:
 		(git checkout $${branch} && npm install && VUEPRESS_BASE="/$${path_prefix}/" npm run build) ; \
 		mkdir -p ~/output/$${path_prefix} ; \
 		cp -r .vuepress/dist/* ~/output/$${path_prefix}/ ; \
-		# Note: the last entry inside the `versions` file will be the default root index.html.
 		cp ~/output/$${path_prefix}/index.html ~/output ; \
 	done < versions ;