Change the Hash.to_xml with a lamda example

[JustinJruby]

Summary

Update the hash.to_xml example (with a lambda) to be more clear

The existing example isn't clear on how it works. The documentation is talking about how Hash.to_xml is used but the example makes it look like it's something to do with string.to_xml. And it raises the question why the lambda is used.

I updated the example to be more in line with what is being exampled.

Other Information

Update 'foo'.to_xml(lambda { |options, key| options[:builder].b(key) })
to {foo: lambda { |options, key| options[:builder].b(key) }}.to_xml

[rails-bot]

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @kaspth (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[maclover7]

👍 Thank you for your contribution!

[maclover7]

❤️ 💚 💙 💛 💜

In the future, please add [ci skip] to any commits that involve changing the documentation, to avoid running the entire Rails test suite.

[JustinJruby]

Thanks!