workflows: remove flake-check and flake-update

Removing to rewrite with improvements.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/flake-check.yaml

@@ -1,14 +0,0 @@
-name: Run nix flake check
-on:
-  push:
-  pull_request:
-
-jobs:
-  flake-check:
-    runs-on: ubuntu-latest
-    container:
-      image: ghcr.io/catthehacker/ubuntu:runner-latest
-    steps:
-      - uses: actions/checkout@v3
-      - uses: cachix/install-nix-action@v27
-      - run: nix flake check

.github/workflows/flake-update.yaml

@@ -1,27 +0,0 @@
----
-name: Periodic flake update
-on:  # yamllint disable-line rule:truthy
-  schedule:
-    - cron: "0 0 * * *"
-
-permissions:
-  contents: write
-
-jobs:
-  flake-update:
-    runs-on: ubuntu-latest
-    container:
-      image: ghcr.io/catthehacker/ubuntu:runner-latest
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          ref: master
-      - uses: cachix/install-nix-action@v27
-      - name: configure git
-        run: |
-          git config --global user.name 'torjus-bot'
-          git config --global user.email 'torjus-bot@git.t-juice.club'
-      - name: flake update
-        run: nix flake update --commit-lock-file
-      - name: push
-        run: git push