bump test-docs image

maybe this fixes the build

Author: minrk

.github/workflows/test-docs.yml

@@ -26,13 +26,13 @@ env:
 
 jobs:
   test-docs:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
 
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
           cache: pip
 
       - name: Install libzmq