Delete ACME files

Let's Encrypt certificates are now managed by GitLab. No need to keep those files anymore.
1 job for remove-acme-challenge-files in 1 minute and 19 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
failed #260846931
dist

00:01:19

 
Name Stage Failure
failed
dist Build
dist/blog/2015-07-29-react-component-testing.html                                 1.02 KB     277ms
dist/blog/2017-08-04-weird-aws-region-bug.html 905 B 258ms
dist/solarized-light.7ab080db.css 836 B 444ms
dist/blog/2017-06-29-managing-access-to-npm-private-packages.html 205 B 271ms
cp -r .well-known/ dist/.well-known/
cp: cannot stat '.well-known/': No such file or directory
Makefile:25: recipe for target 'dist' failed
make: *** [dist] Error 1
ERROR: Job failed: exit code 1