Update gpgme to v2.0.24

What does this MR do and why?

This update adds some methods (https://github.com/ueno/ruby-gpgme/pull/180) and reduces the size of installs since cleanup now works properly (https://github.com/ueno/ruby-gpgme/pull/178).

Diff: https://my.diffend.io/gems/gpgme/2.0.23/2.0.24

How to set up and validate locally

1. Go to the -/user_settings/gpg_keys page and add a GPG key.
2. Make sure the e-mail address associated with the GPG key is a Verified e-mail address in the profile.
3. Check out a project, make a signed commit, and push..
4. Go the repository and ensure it shows up as Verified.