Bump net-imap from 0.5.0 to 0.5.1

Bumps [net-imap](https://github.com/ruby/net-imap) from 0.5.0 to 0.5.1.
- [Release notes](https://github.com/ruby/net-imap/releases)
- [Commits](ruby/net-imap@v0.5.0...v0.5.1)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -275,7 +275,7 @@ GEM
       rails (>= 3.2.0)
     net-http (0.5.0)
       uri
-    net-imap (0.5.0)
+    net-imap (0.5.1)
       date
       net-protocol
     net-pop (0.1.2)