Remove All-Contributors (#576)

* Remove from README

* Remove from merged-notification workflow

* Remove .all-contributorsrc

Author: JasonEtco

.all-contributorsrc

@@ -13,7 +13,5 @@ jobs:
             github.issues.createComment({
               ...context.repo,
               issue_number: context.payload.pull_request.number,
-              body: `Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours.
-              
-              If you haven't already, you can add yourself to [the list of contributors](https://github.com/github/docs#contributors-) by creating a new comment in this PR using [these instructions](https://allcontributors.org/docs/en/bot/usage#commands). Thanks again! :sparkles:`
+              body: 'Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours.'
             })