fix: Broken tests missing meta.fixable property

[Brianzchen]

After checking out the code and running tests many fail because they are missing the fixable property. My team is looking to contribute so this will be a first pass cleanup.

Also want to note that https://github.com/gajus/eslint-plugin-flowtype/blob/master/CONTRIBUTING.md#submitting-a-pr the create readme script doesn't work in my branch? I get this error

➜  eslint-plugin-flowtype git:(fix-tests-meta) npm run create-readme

> eslint-plugin-flowtype@0.0.0-development create-readme /Users/brianchen/projects/eslint-plugin-flowtype
> gitdown ./.README/README.md --output-file ./README.md && npm run documentation-add-assertions

(node:89886) UnhandledPromiseRejectionWarning: Error: Branch ("fix-tests-meta") definition does not exist in the config.
    at Object.gitinfo.getRemoteUrl (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitinfo/dist/gitinfo.js:100:13)
    at Object.gitinfo.getUsername (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitinfo/dist/gitinfo.js:132:53)
    at Object.gitinfo.getGithubUrl (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitinfo/dist/gitinfo.js:51:44)
    at Object.helper.compile (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitdown/dist/helpers/gitinfo.js:36:41)
    at Object.gitdown.resolveURLs (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitdown/dist/gitdown.js:111:35)
    at Object.gitdown.get (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitdown/dist/gitdown.js:54:19)
    at async Object.gitdown.writeFile (/Users/brianchen/projects/eslint-plugin-flowtype/node_modules/gitdown/dist/gitdown.js:66:26)
(node:89886) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:89886) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

> eslint-plugin-flowtype@0.0.0-development documentation-add-assertions /Users/brianchen/projects/eslint-plugin-flowtype
> babel-node ./src/bin/addAssertions

@gajus

[gajus]

🎉 This PR is included in version 5.2.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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