Remove ready for review action (#501)

I tried what I could, but I don't think this action will work while Carbon is private.

"Error: Resource not accessible by integration"
https://github.com/carbon-language/carbon-lang/runs/2441129284?check_suite_focus=true

I'd seen this mentioned on some actions:
https://github.com/marketplace/actions/github-project-automation#personal-access-token-secretsgithub_token

However, I thought it might've been a side-effect of the APIs they were using (I did have this running on a local repo), but I think fork PRs are where the problem lies...

.github/workflows/ready_for_review.yaml

@@ -1,20 +0,0 @@
-# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
-# Exceptions. See /LICENSE for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-name: Move ready proposals to RFC
-
-on:
-  pull_request:
-    types: [ready_for_review]
-
-jobs:
-  update-project:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Update project column
-        uses: jonmeow/action-update-project@v1.0
-        with:
-          project_url: https://github.com/carbon-language/carbon-lang/projects/1
-          column_name: RFC
-          github_token: ${{ secrets.GITHUB_TOKEN }}