This is causing locale problems that I can't reproduce locally, but
that still exist, so let's just silence this for now.

Example:

https://gitlab.torproject.org/tpo/tpa/wiki-replica/-/jobs/687276

Excerpt:

$ ./bin/mdl-wrapper $(cat changed-files.txt)
checking file service/donate.md...
/usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl/doc.rb:39:in `split': invalid byte sequence in US-ASCII (ArgumentError)
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl/doc.rb:39:in `initialize'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl/doc.rb:50:in `new'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl/doc.rb:50:in `new_from_file'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl.rb:91:in `block in run'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl.rb:83:in `each'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/lib/mdl.rb:83:in `run'
	from /usr/share/rubygems-integration/all/gems/mdl-0.13.0/bin/mdl:10:in `<top (required)>'
	from /usr/bin/mdl:25:in `load'
	from /usr/bin/mdl:25:in `<main>'

This reverts commit 3b2ba6cb.