Revert "Add .d.ts files from DefinitelyTyped"

This reverts commit be6cd67.

# Conflicts:
#	src/index.d.ts
#	src/language/ast.d.ts

README.md

@@ -141,32 +141,3 @@ Changes are tracked as [GitHub releases](https://github.com/graphql/graphql-js/r
 ### License
 
 GraphQL.js is [MIT-licensed](https://github.com/graphql/graphql-js/blob/master/LICENSE).
-
-### Credits
-
-The `.d.ts` files in this project are, in part, from `@types/graphql`, written by:
-
-- TonyYang https://github.com/TonyPythoneer
-- Caleb Meredith https://github.com/calebmer
-- Dominic Watson https://github.com/intellix
-- Firede https://github.com/firede
-- Kepennar https://github.com/kepennar
-- Mikhail Novikov https://github.com/freiksenet
-- Ivan Goncharov https://github.com/IvanGoncharov
-- Hagai Cohen https://github.com/DxCx
-- Ricardo Portugal https://github.com/rportugal
-- Tim Griesser https://github.com/tgriesser
-- Dylan Stewart https://github.com/dyst5422
-- Alessio Dionisi https://github.com/adnsio
-- Divyendu Singh https://github.com/divyenduz
-- Brad Zacher https://github.com/bradzacher
-- Curtis Layne https://github.com/clayne11
-- Jonathan Cardoso https://github.com/JCMais
-- Pavel Lang https://github.com/langpavel
-- Mark Caudill https://github.com/mc0
-- Martijn Walraven https://github.com/martijnwalraven
-- Jed Mao https://github.com/jedmao
-
-And licensed under the [MIT License](https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/LICENSE).
-
-Thanks to all the above contributors!