[Chore]: Update workflow to run on ruby 3.4, and drop EOL ruby versions

[vcsjones]

1. This adds ruby 3.4 to our run matrix.
2. This drops 2.7 and 3.0. They are EOL.
3. Update the ruby/setup-ruby action with a new pinned SHA that supports Ruby 3.4.x.
4. Increase the minimum ruby version, and bump the gem version to 2.0.

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[rzhade3]

@vcsjones Given that we're no longer supporting anything < 3.1 after this PR, might we want to update the minimum supported Ruby version in the Gemspec file as well?

ssh_data/ssh_data.gemspec

Line 12 in a322517

s.required_ruby_version = ">= 2.3"

[vcsjones]

@rzhade3 I think that is reasonable. It constitutes a breaking change, so we might as well bump the gem version to 2.0 while we are here.