Bump mail from 2.5.4 to 2.5.5

Bumps [mail](https://github.com/mikel/mail) from 2.5.4 to 2.5.5.
- [Release notes](https://github.com/mikel/mail/releases)
- [Changelog](https://github.com/mikel/mail/blob/2.5.5/CHANGELOG.rdoc)
- [Commits](mikel/mail@2.5.4...2.5.5)

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

Author: dependabot[bot]

Gemfile.lock

@@ -58,15 +58,15 @@ GEM
       railties (>= 3.0, < 5.0)
       thor (>= 0.14, < 2.0)
     json (1.8.6)
-    mail (2.5.4)
+    mail (2.5.5)
       mime-types (~> 1.16)
       treetop (~> 1.4.8)
-    mime-types (1.24)
+    mime-types (1.25.1)
     minitest (4.7.5)
     multi_json (1.15.0)
     orm_adapter (0.4.0)
     pg (0.16.0)
-    polyglot (0.3.3)
+    polyglot (0.3.5)
     rack (1.5.2)
     rack-test (0.6.2)
       rack (>= 1.0)