bump ci python to 3.13

Author: hoxbro

.github/workflows/ipywidgets-bokeh-ci.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         node-version: [20.x]
-        python-version: ["3.12"]
+        python-version: ["3.13"]
 
     defaults:
       run: