Update mime-types to v3.3.1

This fixes some Ruby 2.7 warnings:

```
ruby/2.7.0/gems/mime-types-3.1/lib/mime/types/logger.rb:28: warning: `_1' is reserved for numbered parameter; consider another name
ruby/2.7.0/gems/mime-types-3.1/lib/mime/types/logger.rb:28: warning: `_2' is reserved for numbered parameter; consider another name
ruby/2.7.0/gems/mime-types-3.1/lib/mime/types/logger.rb:28: warning: `_3' is reserved for numbered parameter; consider another name
```

This is also the version we use in GitLab EE/CE.

Gemfile.lock

@@ -218,9 +218,9 @@ GEM
     memoizable (0.4.2)
       thread_safe (~> 0.3, >= 0.3.1)
     method_source (0.9.2)
-    mime-types (3.1)
+    mime-types (3.3.1)
       mime-types-data (~> 3.2015)
-    mime-types-data (3.2016.0521)
+    mime-types-data (3.2020.0512)
     mini_portile2 (2.3.0)
     minitar (0.9)
     mixlib-archive (1.0.5)