fix: added FlowFixMe on Array.prototype.flatMap

[Michael-M-Judd]

• Fix for flow-bin 0.96, which complains about flatMap not existing.

When on flow-bin 0.96, we get flow complaints with the flatMap polyfill:

Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ node_modules/graphql/polyfills/flatMap.js.flow:12:30

Cannot get Array.prototype.flatMap because property flatMap is missing in Array [1].

     node_modules/graphql/polyfills/flatMap.js.flow
       9│ // $FlowFixMe
      10│ const flatMap = Array.prototype.flatMap
      11│   ? function(list, fn) {
      12│       return Array.prototype.flatMap.call(list, fn);
      13│     }
      14│   : function(list, fn) {
      15│       let result = [];

     /private/tmp/flow/flowlib_3d33be40/core.js
 [1] 242│ declare class Array<T> extends $ReadOnlyArray<T> {

I believe line 10, the first $FlowFixMe there does the exact same thing as well. It's worth noting that the latest version of flow-bin does not have this problem.

[IvanGoncharov]

@Michael-M-Judd Thanks for PR 👍
This happened because Flow v0.103.0 finally added flatMap definition and I was too eager in removing $FlowFixMe:
https://github.com/facebook/flow/releases/tag/v0.103.0

Added support for Array#flatMap

[IvanGoncharov]

@Michael-M-Judd I also plan to include a few other fixes and release 14.5.4 today.