Fix typo in README

Signed-off-by: Can Berk Güder <cbg@cbg.me>

README.md

@@ -434,7 +434,7 @@ metrics_app = make_asgi_app()
 app.mount("/metrics", metrics_app)
 ```
 
-For Multiprocessing support, use this modified code snippet. Full multiprocessing intstructions are provided [here](https://github.com/prometheus/client_python#multiprocess-mode-eg-gunicorn).
+For Multiprocessing support, use this modified code snippet. Full multiprocessing instructions are provided [here](https://github.com/prometheus/client_python#multiprocess-mode-eg-gunicorn).
 
 ```python
 from fastapi import FastAPI