Bump net-imap from 0.5.1 to 0.5.6 (#877)

Bumps [net-imap](https://github.com/ruby/net-imap) from 0.5.1 to 0.5.6.
- [Release notes](https://github.com/ruby/net-imap/releases)
- [Commits](ruby/net-imap@v0.5.1...v0.5.6)

---
updated-dependencies:
- dependency-name: net-imap
  dependency-type: indirect
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -167,7 +167,7 @@ GEM
     mini_mime (1.1.5)
     mini_portile2 (2.8.8)
     minitest (5.25.4)
-    net-imap (0.5.1)
+    net-imap (0.5.6)
       date
       net-protocol
     net-pop (0.1.2)
@@ -272,7 +272,7 @@ GEM
     sqlite3 (2.4.1-x86_64-linux-gnu)
     stringio (3.1.2)
     thor (1.3.2)
-    timeout (0.4.2)
+    timeout (0.4.3)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     useragent (0.16.11)