Bump net-imap from 0.4.12 to 0.4.13

Bumps [net-imap](https://github.com/ruby/net-imap) from 0.4.12 to 0.4.13.
- [Release notes](https://github.com/ruby/net-imap/releases)
- [Commits](https://github.com/ruby/net-imap/compare/v0.4.12...v0.4.13)

---
updated-dependencies:
- dependency-name: net-imap
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -273,7 +273,7 @@ GEM
       uri
     net-http-persistent (4.0.2)
       connection_pool (~> 2.2)
-    net-imap (0.4.12)
+    net-imap (0.4.13)
       date
       net-protocol
     net-pop (0.1.2)