Maintenance: Update dependency graphql to v2.0.20

Gemfile.lock

@@ -222,7 +222,7 @@ GEM
       activesupport (>= 5.0)
     gmail_xoauth (0.4.2)
       oauth (>= 0.3.6)
-    graphql (2.0.19)
+    graphql (2.0.20)
     graphql-batch (0.5.2)
       graphql (>= 1.10, < 3)
       promise.rb (~> 0.7.2)