Workaround for Ruby's warning in YARD

This is a workaround to prevent the following warning in YARD:

```console
$ ruby -v
ruby 3.4.0dev (2024-06-14T03:14:32Z master 2677ab1607) [x86_64-darwin23]
$ cd path/to/rubocop
$ bundle exec rake
/Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+0/gems/yard-0.9.36/lib/yard/logging.rb:3:
warning: logger was loaded from the standard library, but will no longer be part of the default gems since Ruby 3.5.0.
Add logger to your Gemfile or gemspec.
```

The fundamental resolution will likely be addressed in lsegal/yard#1546.

Gemfile

@@ -7,6 +7,10 @@ gemspec
 gem 'asciidoctor'
 gem 'bump', require: false
 gem 'bundler', '>= 1.15.0', '< 3.0'
+# FIXME: This is a workaround to prevent the following warning in YARD:
+# https://github.com/lsegal/yard/pull/1546
+# Please remove this dependency when the issue is resolved.
+gem 'logger'
 gem 'memory_profiler', platform: :mri
 # FIXME: This is a workaround to prevent the following warning in YARD:
 # https://github.com/lsegal/yard/pull/1545