Use correct URL for RERUN_NOTEBOOK_ASSET (#9800)

- Fixes: #9799

Author: jleibs

rerun_notebook/src/rerun_notebook/__init__.py

@@ -41,7 +41,7 @@
     if "RERUN_DEV_ENVIRONMENT" in os.environ:
         ASSET_ENV = "serve-local"
     else:
-        ASSET_ENV = "https://app.rerun.io/version/{__version__}/widget.js"
+        ASSET_ENV = f"https://app.rerun.io/version/{__version__}/widget.js"
 
 if ASSET_ENV == ASSET_MAGIC_SERVE:
     from .asset_server import serve_assets