Remove temporary codemod script

This reverts the codemod script and ESLint config I added temporarily
in order to perform the invariant codemod.

.eslintrc.js

@@ -249,16 +249,6 @@ module.exports = {
         TaskController: true,
       },
     },
-    // TODO: I'm adding this plugin to the repo temporarily, but I'll revert it
-    // in the same PR. That way we don't have to check it in but it's still
-    // accessible (via the PR) if we need it later.
-    {
-      files: ['packages/**/*.js'],
-      plugins: ['unused-imports'],
-      rules: {
-        'unused-imports/no-unused-imports': ERROR,
-      },
-    },
   ],
 
   globals: {

package.json

@@ -61,7 +61,6 @@
     "eslint-plugin-no-function-declare-after-return": "^1.0.0",
     "eslint-plugin-react": "^6.7.1",
     "eslint-plugin-react-internal": "link:./scripts/eslint-rules",
-    "eslint-plugin-unused-imports": "^1.1.5",
     "fbjs-scripts": "1.2.0",
     "filesize": "^6.0.1",
     "flow-bin": "0.97",

yarn.lock

@@ -6447,7 +6447,6 @@ eslint-plugin-no-unsanitized@3.1.2:
 
 "eslint-plugin-react-internal@link:./scripts/eslint-rules":
   version "0.0.0"
-  uid ""
 
 eslint-plugin-react@^6.7.1:
   version "6.10.3"
@@ -6460,13 +6459,6 @@ eslint-plugin-react@^6.7.1:
     jsx-ast-utils "^1.3.4"
     object.assign "^4.0.4"
 
-eslint-plugin-unused-imports@^1.1.5:
-  version "1.1.5"
-  resolved "https://registry.yarnpkg.com/eslint-plugin-unused-imports/-/eslint-plugin-unused-imports-1.1.5.tgz#a2b992ef0faf6c6c75c3815cc47bde76739513c2"
-  integrity sha512-TeV8l8zkLQrq9LBeYFCQmYVIXMjfHgdRQLw7dEZp4ZB3PeR10Y5Uif11heCsHRmhdRIYMoewr1d9ouUHLbLHew==
-  dependencies:
-    eslint-rule-composer "^0.3.0"
-
 eslint-rule-composer@^0.3.0:
   version "0.3.0"
   resolved "https://registry.yarnpkg.com/eslint-rule-composer/-/eslint-rule-composer-0.3.0.tgz#79320c927b0c5c0d3d3d2b76c8b4a488f25bbaf9"