modify the contributing guide a tad bit to use uv run python -m reflex.utils.pyi_generator (#5576)

Author: adhami3310

CONTRIBUTING.md

@@ -108,5 +108,5 @@ For some pull requests when adding new components you will have to generate a py
 (Please check in with the team before adding a new component to Reflex we are cautious about adding new components to Reflex's core.)
 
 ```bash
-uv run python scripts/make_pyi.py
+uv run python -m reflex.utils.pyi_generator
 ```