switch back to bootstrap 3 in attempt to get dataspy working

2 jobs for dataspy-hacking in 21 seconds (queued for 2 seconds)
Status Job ID Name Coverage
canceled deadlinks #19721
allowed to fail


failed test #19720


Name Stage Failure
test Test There is an unknown failure, please try again
If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.
Git error: command `git reset --hard 867c1f71c4a0f76e08cceb2b2a012243c83ecceb`
in directory /home/gitlab-runner/gems/bundler/gems/jekyll-scholar-867c1f71c4a0
has failed.
If this error persists you could try removing the cache directory
ERROR: Job failed: exit status 1