Replaced deprecated httpx param data with content (#1945)

Fixes #1944

Author: rayokota

src/confluent_kafka/schema_registry/schema_registry_client.py

@@ -484,7 +484,7 @@ def send_http_request(
         for i in range(self.max_retries + 1):
             response = self.session.request(
                 method, url="/".join([base_url, url]),
-                headers=headers, data=body, params=query)
+                headers=headers, content=body, params=query)
 
             if is_success(response.status_code):
                 return response