Merge pull request #449 from citizensadvice/dependabot/bundler/net-imap-0.6.4

[dependabot:bundler] bump net-imap from 0.6.3 to 0.6.4

Author: marianayovcheva

Gemfile.lock

@@ -214,7 +214,7 @@ GEM
       prism (~> 1.5)
     msgpack (1.8.0)
     multi_json (1.15.0)
-    net-imap (0.6.3)
+    net-imap (0.6.4)
       date
       net-protocol
     net-pop (0.1.2)