Multiple references to missing PATENTS file

[copiesofcopies]

Several files in the project contain some version of the following license header:

/**

• Copyright (c) 2021 GraphQL Contributors
• All rights reserved.
• This source code is licensed under the BSD-style license found in the
• LICENSE file in the root directory of this source tree. An additional grant
• of patent rights can be found in the PATENTS file in the same directory.
  */

However, no PATENTS file exists anywhere in the repository. Maybe a vestige of a former license? I suggest updating these headers to remove the reference to the PATENTS file.