chore: empty payload in info requests to agent (#5245)

This change ensures that we send an empty payload to the agent when
performing info requests, to conform with what the system tests expect.

Author: P403n1x87

ddtrace/internal/agent.py

@@ -153,7 +153,7 @@ def info():
     agent_url = get_trace_url()
     _conn = get_connection(agent_url, timeout=get_trace_agent_timeout())
     try:
-        _conn.request("GET", "info", "{}", {"content-type": "application/json"})
+        _conn.request("GET", "info", headers={"content-type": "application/json"})
         resp = _conn.getresponse()
         data = resp.read()
     finally: