Mark localEcho settings as preview

Part of microsoft/vscode#126209
See microsoft/vscode#239335

Author: Tyriar

docs/terminal/advanced.md

@@ -196,7 +196,11 @@ Since ConPTY is an emulation layer, it does come with some quirks. The most comm
 
 This section outlines topics specific to when VS Code is connected to a remote machine using a VS Code [Remote Development](https://code.visualstudio.com/docs/remote/remote-overview) extension.
 
-### Reducing remote input latency
+### Local terminals in remote windows
+
+The default **local** terminal profile can be launched in remote windows with the **Terminal: Create New Integrated Terminal (Local)** command via the Command Palette. Currently non-default profiles cannot be launched from remote windows.
+
+### Reducing remote input latency (Preview)
 
 Local echo is a feature that helps mitigate the effect of input latency on remote windows. It writes the keystrokes in the terminal in a dimmed color before the result is confirmed by the remote. By default, the feature start running when latency is detected to be above 30 ms and the timing can be configured with `setting(terminal.integrated.localEchoLatencyThreshold)`. The color of the unconfirmed characters is defined by `setting(terminal.integrated.localEchoStyle)`.
 
@@ -209,7 +213,3 @@ To disable the feature completely, use:
   "terminal.integrated.localEchoEnabled": false
 }
 ```
-
-### Local terminals in remote windows
-
-The default **local** terminal profile can be launched in remote windows with the **Terminal: Create New Integrated Terminal (Local)** command via the Command Palette. Currently non-default profiles cannot be launched from remote windows.