goenv: don't inreplace init.bats on HEAD installs

[stephengroat]

init.bats no longer exists

see go-nv/goenv#80 (comment)

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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[carlocab]

It still exists in the stable tarball. Please restrict removing it to --HEAD installs only.

[carlocab]

Thanks, @stephengroat. Cleaned this up a little for you.

[vidhanio]

Thanks for fixing this up! 😄 ❤️

[carlocab]

Oops; made a mistake while fixing it up. Fixed now.