dev-cmd/edit: Show API install warning after the edit is done

[abitrolly]

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brew edit ocp outputs this text when the editor is opened.

$ brew edit ocp
Warning: `brew install` ignores locally edited casks and formulae if
HOMEBREW_NO_INSTALL_FROM_API is not set.
Editing /home/linuxbrew/.linuxbrew/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/o/ocp.rb
Warning: Using vim because no editor was set in the environment.
This may change in the future, so we recommend setting EDITOR
or HOMEBREW_EDITOR to your preferred text editor.

The PR moves the first warning so that it is shown only when the edit is finished.

[MikeMcQuaid]

Why is it better for this to be after rather than before?

[abitrolly]

Because the message about "brew install" doesn't make too much sense when user invokes "brew edit". Only if the edit is successful. The next step is to improve the message with the actual command to test the edit.

[MikeMcQuaid]

Thanks @abitrolly!