test/rubocops/formula_desc: Ensure autocorrect when `desc` ends in `.`
test/rubocops/formula_desc: Ensure autocorrect when `desc` ends in `.`

- This was another thing that I should have done in PR 3411 in 2017,
  tested that the regex for autocorrecting `desc` stanzas ending in full
  stops actually worked. At least I'm getting to it now.

Homebrew/brew,Homebrew/brew,Homebrew/brew,nandub/brew,nandub/brew,Homebrew/brew,nandub/brew,nandub/brew