remove bot token, and use secrets.GITHUB_TOKEN instead (#200)

* is symfembot still needed?

* secrets.GITHUB_TOKEN

Author: mscroggs

.github/workflows/run-tests.yml

@@ -26,15 +26,5 @@ jobs:
         name: Run flake8 on tests
       - run: flake8 _tools/
         name: Run flake8 on tools
-      - run: |
-          TOKEN=${{ secrets.symfembot_token }}
-          if [ -n "${TOKEN}" ]; then
-            echo "token=${TOKEN}" >> ${GITHUB_OUTPUT}
-          else
-            echo "token=${{ github.token }}" >> ${GITHUB_OUTPUT}
-          fi
-        shell: bash
-        name: Determine which token to use when running tests
-        id: token
-      - run: GITHUB_TOKEN=${{ steps.token.outputs.token }} python3 -m pytest _test/ --has-fenicsx 1
+      - run: GITHUB_TOKEN=${{ secrets.GITHUB_TOKEN }} python3 -m pytest _test/ --has-fenicsx 1
         name: Run tests