Docs: fix the CI that build the doc

2 jobs for 2.1.2 in 8 minutes and 30 seconds
Name Stage Failure
pages Deploy
Reinitialized existing Git repository in /builds/verimag/synchrone/sasa/.git/
Fetching changes...
Checking out 4d2f2706 as 2.1.2...

Skipping Git submodules setup
$ cd guides/users
$ make
make: *** No targets specified and no makefile found. Stop.
ERROR: Job failed: exit code 1