Revert "Remove master from versions and copy it from the latest." (backport #8053) (#8057)

This reverts commit f939f962b1.

A lot of inbound links are still broken, so we will need to find a different
approach to suppressing unreleased docs.

(cherry picked from commit 59eaa4dba0)

Makefile

@@ -221,9 +221,7 @@ build-docs:
 		mkdir -p ~/output/$${path_prefix} ; \
 		cp -r .vuepress/dist/* ~/output/$${path_prefix}/ ; \
 		cp ~/output/$${path_prefix}/index.html ~/output ; \
-	done < versions ; \
-	mkdir -p ~/output/master ; \
-	cp -r .vuepress/dist/* ~/output/master/
+	done < versions ;
 .PHONY: build-docs
 
 ###############################################################################

docs/versions

@@ -1,3 +1,4 @@
+master                  master
 v0.33.x                 v0.33
 v0.34.x                 v0.34
 v0.35.x                 v0.35