agent: Update use_modifier_to_send behavior description for Windows (#36230)

Release Notes:

- N/A

Signed-off-by: Yang Gang <yanggang.uefi@gmail.com>

crates/agent_settings/src/agent_settings.rs

@@ -309,7 +309,7 @@ pub struct AgentSettingsContent {
     ///
     /// Default: true
     expand_terminal_card: Option<bool>,
-    /// Whether to always use cmd-enter (or ctrl-enter on Linux) to send messages in the agent panel.
+    /// Whether to always use cmd-enter (or ctrl-enter on Linux or Windows) to send messages in the agent panel.
     ///
     /// Default: false
     use_modifier_to_send: Option<bool>,