bump-revision: fixes for new style and license dsl

[Rylan12]

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After #7953, formula.license returns an array even when only one license is specified. This PR adds logic to check whether there is more than one license and formats the license line appropriately.

Additionally, #7867 changed the style for revision from :revision => "..." to revision: "...". This PR also handles that.

[MikeMcQuaid]

Assuming you've tested locally for both paths and it works as expected: ! Thanks @Rylan12!

[Rylan12]

I think I've covered everything:

• qt: no license line
• vim: single license
• vim (modified): multiple licenses (none exist in homebrew-core yet so I just added a fake one)
• volt: no license line and has a revision: "..." line