fix: Send display_name when creating a sandbox environment template.

The `display_name` parameter of the sandbox template create method was routed
with `_parent.*`, but it is a top-level request parameter with no parent object,
so it was silently dropped from the request body (never sent to the backend).
Route it to the request body (`*`) so `display_name` is correctly included.

PiperOrigin-RevId: 952240948

Author: vertex-sdk-bot

agentplatform/_genai/sandbox_templates.py

@@ -79,7 +79,7 @@ def _CreateSandboxEnvironmentTemplateRequestParameters_to_vertex(
         )
 
     if getv(from_object, ["display_name"]) is not None:
-        setv(parent_object, ["displayName"], getv(from_object, ["display_name"]))
+        setv(to_object, ["displayName"], getv(from_object, ["display_name"]))
 
     return to_object