Remove CI graph generation

Signed-off-by: AKU <tom@tdpain.net>

.github/workflows/update-running-time-graph.yml

@@ -1,35 +0,0 @@
-name: Update running time graph
-
-on:
-  workflow_dispatch:
-  schedule:
-    - cron: "58 4 * 12 *"
-
-jobs:
-  graph:
-      runs-on: ubuntu-latest
-      steps:
-        - name: Check out repository
-          uses: actions/checkout@v2
-          with:
-            ref: ${{ github.ref }}
-            fetch-depth: 0
-
-        - name: Setup Python
-          uses: actions/setup-python@v2
-          with:
-            python-version: '3.x'
-
-        - name: Install Matplotlib
-          run: pip install matplotlib
-
-        - name: Run script  
-          run: python generate-benchmark-graph.py challenges/2021/runtime-graph.png 2021
-
-        - name: Git commit and push
-          run: |
-            git config user.email 'actions@github.com'
-            git config user.name 'github-actions'
-            git add challenges/2021/runtime-graph.png
-            git commit -m 'Update running time graph'
-            git push origin HEAD:${{ github.ref }}