Remove defunct github actions workflows (#7027)

These workflows relied on old-style Personal Access Tokens. They've been
disabled for a while, and we have no intention of re-enabling them. The
add-to-project workflow in particular has been fully replaced by
Projects-native features.

.github/workflows/add-to-project.yml

@@ -1,16 +0,0 @@
-name: Add new bugs to triage project
-
-on:
-  issues:
-    types:
-      - opened
-
-jobs:
-  add-to-project:
-    name: Add issue to triage project
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/add-to-project@main
-        with:
-          project-url: https://github.com/orgs/letsencrypt/projects/6
-          github-token: ${{ secrets.ADD_TO_PROJECT_PAT }}

.github/workflows/update-psl.yml

@@ -1,58 +0,0 @@
-name: Update PSL
-
-on:
-  workflow_dispatch:
-  schedule:
-    # Run monthly at a random (https://xkcd.com/221/) time.
-    - cron: '46 16 1 * *'
-
-permissions:
-  contents: write
-  pull-requests: write
-
-jobs:
-  create-pr:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-
-      # This is the real username and email used by github-actions elsewhere.
-      - run: git config user.name "github-actions[bot]"
-      - run: git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
-
-      - run: echo ::set-output name=name::update-psl-$(date +%F)
-        id: branch
-
-      - run: git checkout -b ${{ steps.branch.outputs.name }}
-
-      # We run these inside "docker compose" to ensure we use the same Go version
-      # as elsewhere. They're run inside the netaccess container so they can
-      # download the dependency files.
-      - run: docker compose run netaccess go get github.com/weppos/publicsuffix-go@main
-      - run: docker compose run netaccess go mod vendor
-      - run: docker compose run netaccess go mod tidy
-
-      - run: git diff --numstat vendor/github.com/weppos/publicsuffix-go/publicsuffix/rules.go | awk '{ print "::set-output name=body::" $1 " additions and " $2 " removals." }'
-        id: diff
-
-      - run: git add vendor go.mod go.sum
-      - run: git commit -m "Update Public Suffix List"
-      - run: git push origin ${{ steps.branch.outputs.name }}
-
-      - run: echo ::set-output name=name::$(gh repo view --json defaultBranchRef --jq .defaultBranchRef.name)
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        id: default_branch
-
-      - uses: actions/github-script@v6
-        with:
-          github-token: ${{ secrets.CREATE_PR_PAT }}
-          script: |
-            github.rest.pulls.create({
-              title: 'Update Public Suffix List',
-              body: '${{ steps.diff.outputs.body }}',
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              head: '${{ steps.branch.outputs.name }}',
-              base: '${{ steps.default_branch.outputs.name }}'
-            })