Maintenance: Update dependency net-imap to v0.5.2

Gemfile.lock

@@ -373,7 +373,7 @@ GEM
       time
     net-http (0.6.0)
       uri
-    net-imap (0.5.1)
+    net-imap (0.5.2)
       date
       net-protocol
     net-ldap (0.19.0)
@@ -682,7 +682,7 @@ GEM
     tilt (2.4.0)
     time (0.4.0)
       date
-    timeout (0.4.2)
+    timeout (0.4.3)
     tpm-key_attestation (0.12.1)
       bindata (~> 2.4)
       openssl (> 2.0)