fix: only send load balancer service health_check properties when defined (#691)

The code was sending all the health_check properties unconditionally,
which prevented from falling back on API defaults or to partially update
the health_check values.

Author: jooola

hcloud/load_balancers/domain.py

@@ -222,13 +222,7 @@ def to_payload(self) -> dict[str, Any]:
             payload["http"] = http
 
         if self.health_check is not None:
-            health_check: dict[str, Any] = {
-                "protocol": self.health_check.protocol,
-                "port": self.health_check.port,
-                "interval": self.health_check.interval,
-                "timeout": self.health_check.timeout,
-                "retries": self.health_check.retries,
-            }
+            health_check: dict[str, Any] = {}
             if self.health_check.protocol is not None:
                 health_check["protocol"] = self.health_check.protocol
             if self.health_check.port is not None: