prof: needs at least 1 argument

[jonchang]

brew prof was incorrectly marked as having an optional argument, which is not correct as a bare brew prof will result in:

% brew prof
Error: undefined method `extname' for nil:NilClass
Please report this issue:
  https://docs.brew.sh/Troubleshooting
/usr/local/Homebrew/Library/Homebrew/dev-cmd/prof.rb:30:in `prof'
/usr/local/Homebrew/Library/Homebrew/brew.rb:122:in `<main>'

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[BrewTestBot]

Review period will end on 2021-02-16 at 00:00:00 UTC.

[MikeMcQuaid]

Thanks @jonchang!

[BrewTestBot]

Review period skipped due to critical label.