Use git HEAD of the warning gem

[dentarg]

Until jeremyevans/ruby-warning#24 finds its way into a relase

What's a little bit strange it that there's still one :default_gem_removal warning shown:

This PR

$ b e rake
Run options: --seed 33480

# Running:

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Finished in 0.029789s, 637.8193 runs/s, 704.9582 assertions/s.

19 runs, 21 assertions, 0 failures, 0 errors, 0 skips
Run options: --seed 18890

# Running:

..................2024-12-17 08:03:39 +0100 Rack app ("GET /" - (127.0.0.1)): #<NoMethodError: undefined method `each' for nil>
./Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
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Finished in 1.930490s, 22.2741 runs/s, 44.5483 assertions/s.

43 runs, 86 assertions, 0 failures, 0 errors, 0 skips
Running RuboCop...
Inspecting 56 files
........................................................

56 files inspected, no offenses detected

but in main that warning we see the above warning is logged 5 times, so the silencing default_gem_removal made some improvement :)

main branch

$ b e rake
/Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
Run options: --seed 21671

# Running:

...................

Finished in 0.028384s, 669.3912 runs/s, 739.8534 assertions/s.

19 runs, 21 assertions, 0 failures, 0 errors, 0 skips
/Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
Run options: --seed 47951

# Running:

................................../Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
./Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
./Users/dentarg/.arm64_rubies/3.3.5/lib/ruby/gems/3.3.0/gems/github-markup-5.0.1/lib/github/markup/rdoc.rb:2: warning: rdoc was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add rdoc to your Gemfile or gemspec to silence this warning.
2024-12-17 08:04:15 +0100 Rack app ("GET /" - (127.0.0.1)): #<NoMethodError: undefined method `each' for nil>
.......

Finished in 1.932265s, 22.2537 runs/s, 44.5074 assertions/s.

43 runs, 86 assertions, 0 failures, 0 errors, 0 skips
Running RuboCop...
Inspecting 56 files
........................................................

56 files inspected, no offenses detected