Bump mail from 2.7.0 to 2.7.1

Bumps [mail](https://github.com/mikel/mail) from 2.7.0 to 2.7.1.
- [Release notes](https://github.com/mikel/mail/releases)
- [Changelog](https://github.com/mikel/mail/blob/master/CHANGELOG.rdoc)
- [Commits](mikel/mail@2.7.0...2.7.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile.lock

@@ -42,7 +42,7 @@ GEM
     json (2.1.0)
     launchy (2.4.3)
       addressable (~> 2.3)
-    mail (2.7.0)
+    mail (2.7.1)
       mini_mime (>= 0.1.1)
     method_source (0.9.0)
     mime-types (3.2.2)