Increase example max depths and mention introspection requirement

Author: rmosolgo

guides/queries/complexity_and_depth.md

@@ -129,13 +129,15 @@ You can also reject queries based on the depth of their nesting. You can define
 # Schema-level:
 class MySchema < GraphQL::Schema
   # ...
-  max_depth 10
+  max_depth 15
 end
 
 # Query-level, which overrides the schema-level setting:
-MySchema.execute(query_string, max_depth: 10)
+MySchema.execute(query_string, max_depth: 20)
 ```
 
+(**Note:** the default introspection query from GraphiQL requires at least `max_depth 13`.)
+
 You can use `nil` to disable the validation:
 
 ```ruby

guides/schema/definition.md

@@ -176,7 +176,7 @@ Then, during execution, `context` will be an instance of `CustomContext`.
 
 ```ruby
 class MySchema < GraphQL::Schema
-  max_depth 10
+  max_depth 15
   max_complexity 300
   default_max_page_size 20
 end