docs: add request_hook parameter description to RedisInstrumentor

Author: nhtgl

instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/__init__.py

@@ -474,6 +474,7 @@ def _instrument(self, **kwargs: Any):
         Args:
             **kwargs: Optional arguments
                 ``tracer_provider``: a TracerProvider, defaults to global.
+                ``request_hook``: An optional callback that is invoked right after a span is created.
                 ``response_hook``: An optional callback which is invoked right before the span is finished processing a response.
         """
         tracer_provider = kwargs.get("tracer_provider")