Kill Flow support

Summary:
* Removed Flow compilation step
* Removed all `flow` annotations
* Removed all FlowFixMe's
* Removed flow typings for Flipper
* Left flow transpilation (stripping) in babel, in case there is any external user using Flow in his plugin
* Left `eslint-plugin-flowtype` dependencies, as `eslint-config-fbjs` requires it

Reviewed By: passy

Differential Revision: D24755545

fbshipit-source-id: 9c0a7910657fd1cba88294e041bf2bfdf7b565bf

desktop/headless-tests/package.json

@@ -19,7 +19,6 @@
   "dependencies": {
     "@babel/core": "^7.11.1",
     "@babel/preset-env": "^7.11.0",
-    "@babel/preset-flow": "^7.10.4",
     "babel-jest": "^26.2.2",
     "canonical-json": "^0.0.4",
     "lodash.memoize": "^4.1.2"