github/copilot: Add python3.12 install for pants (#3101)

Signed-off-by: Ryan Northey <[email protected]>

Author: phlax

.github/workflows/copilot-setup-steps.yml

@@ -85,6 +85,9 @@ jobs:
         bazel --version
       working-directory: bazel
 
+    - uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548  # v6.1.0
+      with:
+        python-version: "3.12"
     - name: Pants
       run: |
         ./get-pants.sh