agent: Rename "open configuration" action to "open settings" (#35329)

"Settings" is the terminology we use in the agent panel, thus having the
action use "configuration" makes it harder for folks to find this either
via the command palette or the keybinding editor UI in case they'd like
to change it.

Release Notes:

- agent: Renamed the "open configuration" action to "open settings" for
better discoverability and consistency

docs/src/ai/mcp.md

@@ -50,7 +50,7 @@ You can connect them by adding their commands directly to your `settings.json`,
 }
 ```
 
-Alternatively, you can also add a custom server by accessing the Agent Panel's Settings view (also accessible via the `agent: open configuration` action).
+Alternatively, you can also add a custom server by accessing the Agent Panel's Settings view (also accessible via the `agent: open settings` action).
 From there, you can add it through the modal that appears when you click the "Add Custom Server" button.
 
 ## Using MCP Servers