ci: remove backport workflow (#339)

.github/workflows/backport.yml

@@ -1,33 +0,0 @@
-# this is based on https://github.com/NixOS/nixpkgs/blob/c81ecdf95b3a0f73ded448f14416cd66beeb5e1a/.github/workflows/backport.yml
-name: Backport
-on:
-  pull_request_target:
-    types: [closed, labeled]
-
-# WARNING:
-# When extending this action, be aware that $GITHUB_TOKEN allows write access to
-# the GitHub repository. This means that it should not evaluate user input in a
-# way that allows code injection.
-
-jobs:
-  backport:
-    name: Backport Pull Request
-    if: github.repository_owner == 'catppuccin' && github.event.pull_request.merged == true && (github.event_name != 'labeled' || startsWith('backport', github.event.label.name))
-
-    runs-on: ubuntu-latest
-
-    permissions:
-      contents: write
-      pull-requests: write
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
-
-      - name: Create backport PRs
-        uses: korthout/backport-action@v3
-        with:
-          pull_description: |-
-            Bot-based backport to `${target_branch}`, triggered by a label in #${pull_number}.