Bump net-imap from 0.5.5 to 0.5.6

Bumps [net-imap](https://github.com/ruby/net-imap) from 0.5.5 to 0.5.6.
- [Release notes](https://github.com/ruby/net-imap/releases)
- [Commits](ruby/net-imap@v0.5.5...v0.5.6)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -176,7 +176,7 @@ GEM
     minitest (5.25.4)
     net-http (0.6.0)
       uri
-    net-imap (0.5.5)
+    net-imap (0.5.6)
       date
       net-protocol
     net-ping (2.0.8)