[BUG] ignore_merge_commits is no longer honored in 6.1.0

[fairbanksg]

Describe the bug
Our cog.toml has ignore_merge_commits = true. After upgrading from 6.0.1 to 6.1.0, this setting seems to be ignored, as we are getting an error about a merge commit not matching the format.

To Reproduce
Include ignore_merge_commits = true in your cog.toml. Push a branch containing a merge commit and attempt to cog bump --auto.

Expected behavior
Version bump should work.

[fairbanksg]

Looking at this more, I think the version bump is actually succeeding, its just that now it is printing out an error message about the merge commit.