Monkey patching libraries is a bad idea.  Latest version of yard changed
some internal details, which broke CI.

A workaround was proposed in #401 but the root cause was not addressed.

In this commit, we replace the private `io` object with an instance of a
class that provide the expected `IO#write` method instead of `nil` which
does not provide this interface in CI, so that the issue is not raised
anymore.

Fix CI with latest yard

puppe is a runtime dependency:

```
$ git grep "require 'puppet/"
lib/puppet-strings/yard/parsers/puppet/parser.rb:require 'puppet/pops'
lib/puppet-strings/yard/parsers/puppet/statement.rb:require 'puppet/pops'
lib/puppet-strings/yard/util.rb:require 'puppet/util'
lib/puppet/application/strings.rb:require 'puppet/application/face_base'
lib/puppet/face/strings.rb:require 'puppet/face'
lib/puppet/feature/rgen.rb:require 'puppet/util/feature'
lib/puppet/feature/yard.rb:require 'puppet/util/feature'
spec/spec_helper.rb:require 'puppet/version'
```

This is part of the OpenVox rebranding. This summary string is part of
the `puppet --help` output.

clarifies the puppet-strings usage

List puppet as runtime dependency

Puppet 7 is EOL. Therefore, we can remove the test infrastructure for it.
This commit aims to clear up any testing/config infrastructure related to
Puppet 7 and, by extension, Ruby 2.7.

…_infrastructure

(CAT-2281) Remove puppet 7 infrastructure

Without this commit, you cannot inform the rake task to push gh-pages to
accept a different commit message. This is necessary in environment
where commit messages have to be in specific formats.

None of the system calls were checking the exit status of their
respective commands. Not stopping on error means that the rake take can
fail and you and your pipelines would not know.

Rake task allows for a different commit message

Release prep v5.0.0