Maintenance: Bump messagebird-rest from 3.1.1 to 4.0.0

Bumps [messagebird-rest](https://github.com/messagebird/ruby-rest-api) from 3.1.1 to 4.0.0.
- [Release notes](https://github.com/messagebird/ruby-rest-api/releases)
- [Changelog](https://github.com/messagebird/ruby-rest-api/blob/master/CHANGELOG.md)
- [Commits](https://github.com/messagebird/ruby-rest-api/compare/3.1.1...4.0.0)

Gemfile.lock

@@ -283,7 +283,7 @@ GEM
     iniparse (1.5.0)
     interception (0.5)
     json (2.6.1)
-    jwt (2.2.3)
+    jwt (2.3.0)
     kgio (2.11.4)
     koala (3.1.0)
       addressable
@@ -306,8 +306,8 @@ GEM
     matrix (0.4.2)
     memoizable (0.4.2)
       thread_safe (~> 0.3, >= 0.3.1)
-    messagebird-rest (3.1.1)
-      jwt (~> 2.2.3)
+    messagebird-rest (4.0.0)
+      jwt (~> 2.3.0)
     method_source (1.0.0)
     mime-types (3.4.1)
       mime-types-data (~> 3.2015)