FEI-4957.8: Remove Flow related plugins, settings, and lib defs (#530)

## Summary:
This removes all Flow relate things.

NOTE: `eslint` is currently not running on .ts files.  I'll fix that in the next PR.

Issue: FEI-4957

## Test plan:
Let CI run the checks

Author: kevinbarabash

Reviewers: jeresig, kevinbarabash

Required Reviewers:

Approved By: jeresig

Checks: ⌛ Test (macos-latest, 16.x), ✅ codecov/project, ✅ CodeQL, ✅ Lint, typecheck, and coverage check (ubuntu-latest, 16.x), ✅ Prime node_modules cache for primary configuration (ubuntu-latest, 16.x), ✅ gerald, ✅ Analyze (javascript), ⏭  dependabot

Pull Request URL: #530

.changeset/eighty-dancers-flash.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/eslint-config": minor
+---
+
+Remove Flow eslint rules

.eslintignore

@@ -1,5 +1,4 @@
 node_modules
-flow-typed/**/*.js
 coverage
 **/dist
 **/*.template

.eslintrc.js

@@ -48,8 +48,6 @@ module.exports = {
         "@babel/no-invalid-this": "error",
         "@babel/object-curly-spacing": "error",
         "@babel/semi": "error",
-        "ft-flow/no-types-missing-file-annotation": "error",
-        "ft-flow/no-existential-type": "error",
         "import/no-default-export": "error",
         "import/no-unresolved": "error",
         "import/named": "error",

.gitignore

@@ -1,6 +1,5 @@
 node_modules
 coverage
-flow-coverage
 dist
 !.vscode
 .DS_Store

.prettierignore

@@ -2,4 +2,3 @@
 *.md
 docs
 *.yml
-flow-typed/npm

.vscode/settings.json

@@ -2,7 +2,6 @@
     "editor.renderWhitespace": "boundary",
     "eslint.codeActionsOnSave.mode": "all",
     "files.trimTrailingWhitespace": true,
-    "flow.useNPMPackagedFlow": true,
     "typescript.format.enable": false,
     "typescript.validate.enable": true,
     "javascript.validate.enable": true,
@@ -11,6 +10,5 @@
     },
     "todo-tree.filtering.excludeGlobs": [
         "**/dist/**",
-        "**/flow-typed/**"
     ]
 }

build-settings/babel.config.js

@@ -1,6 +1,5 @@
 /* eslint-disable import/no-commonjs */
 const createBabelPresets = require("./create-babel-presets");
-const createBabelPlugins = require("./create-babel-plugins");
 
 // This config is used for Jest testing here in this repository, only.
 module.exports = {
@@ -11,8 +10,4 @@ module.exports = {
         platform: "node",
         format: "cjs",
     }),
-    plugins: createBabelPlugins({
-        platform: "node",
-        format: "cjs",
-    }),
 };

build-settings/rollup.config.js

@@ -11,7 +11,6 @@ import {preserveShebangs} from "rollup-plugin-preserve-shebangs";
 import rollupExecutable from "rollup-plugin-executable-output";
 
 const createBabelPresets = require("./create-babel-presets");
-const createBabelPlugins = require("./create-babel-plugins");
 
 /**
  * We support the following config args with this rollup configuration:
@@ -118,7 +117,6 @@ const createConfig = (
             babel({
                 babelHelpers: "bundled",
                 presets: createBabelPresets({platform, format}),
-                plugins: createBabelPlugins({platform, format}),
                 exclude: "node_modules/**",
                 extensions,
             }),