Update mime-types to v3.3.1 for Ruby 2.7

See https://github.com/mime-types/ruby-mime-types/blob/master/History.md

Gemfile.lock

@@ -659,9 +659,9 @@ GEM
       thread_safe (~> 0.3, >= 0.3.1)
     memory_profiler (0.9.14)
     method_source (0.9.2)
-    mime-types (3.2.2)
+    mime-types (3.3.1)
       mime-types-data (~> 3.2015)
-    mime-types-data (3.2019.0331)
+    mime-types-data (3.2020.0512)
     mimemagic (0.3.5)
     mini_histogram (0.1.3)
     mini_magick (4.9.5)