[DOCS] Clarify trusted usage (#18718)

This docs clarifies trusted url requirements

Author: tqchen

docs/reference/security.rst

@@ -43,6 +43,8 @@ The runtime depends on a limited set of system calls(e.g. malloc) in the system
 TVM RPC server assumes that the user is trusted and needs to be used in a trusted network environment
 and encrypted channels. It allows writings of arbitrary files into the server and provide
 full remote code execution capabilities to anyone who can access this API.
+All of the TVM APIs are designed to be used by trusted users, for APIs that involves URL,
+we expect users to put in only trusted URLs.
 
 
 AutoTVM data exchange between the tracker, server and client are in plain-text.