Fix class name for brew extract

[kiendang]

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Fix an oversight in #5868. When run

brew extract --version=1.10.5 kubernetes-cli custom/formulae

class name for [email protected] is KubernetescliAT1105 instead of KubernetesCliAT1105 as expected.

So sorry for not testing this out properly earlier. Wanted to add a test case for this but looks like can't setup_test_formula a formula name with hyphen.

[MikeMcQuaid]

No worries, thanks for the quick fix and thanks again for contributing to Homebrew!