Add language stanza to cask rubocops

[waldyrious]

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These changes have been split out from #8265. The language stanza should be in its own group, but current practice is to separate multiple language blocks with newlines, which contradicts the stanzas within the same group should have no lines between them rule in test/rubocops/cask/stanza_grouping_spec.rb. This PR is kept as a draft until a decision is made in how to address that. For example, we could:

• Edit the casks in Homebrew/Homebrew-cask to remove the blank line between language blocks
• Make an exception for the language stanza in the stanzas within the same group should have no lines between them rule
• Keep the language stanza out of the sorting/grouping validation altogether (as it was before)
• Something else

How should I proceed?

[waldyrious]

/cc @reitermarkus

[reitermarkus]

Edit the casks in Homebrew/homebrew-cask to remove the blank line between language blocks

Done.

Thanks, @waldyrious!

[waldyrious]

That was fast! Thanks again for the quick merge and for editing the casks to match the rule :)