fix: remove trailing newline of commit message

[vaporoxx]

After having experimented with this action for a bit, I found {msg} ({sha}) to be the commit message format I liked the most. However, there seemed to be a trailing newline at the end of the message, converting this example commit message: into this one instead:

I've went through the isomorphic-git source, and found this function which adds a single trailing newline on purpose. I think that it should be removed here though because it ruins the commit message and you can just add it back in your custom commit message if you need it.

[s0]

Thanks for the contribution @vaporox, i'll create a new release shortly