upgrade: fix style in help text

[Rylan12]

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Fix a small spacing issue in the upgrade help text.

Before:

      --formula, --formulae        Treat all named arguments as formulae. If
                                   no named argumentsare specified, upgrade
                                   only outdated formulae.

After:

      --formula, --formulae        Treat all named arguments as formulae. If
                                   no named arguments are specified, upgrade
                                   only outdated formulae.

[BrewTestBot]

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