agent: Fix opening configuration view from the model selector (#28154)

This PR fixes an issue where opening the configuration view from the
model selector in the Agent (or inline assist) was not working properly.

Fixes https://github.com/zed-industries/zed/issues/28078.

Release Notes:

- Agent Beta: Fixed an issue where selecting "Configure" in the model
selector would not bring up the configuration view.

crates/workspace/src/workspace.rs

@@ -127,8 +127,6 @@ static ZED_WINDOW_POSITION: LazyLock<Option<Point<Pixels>>> = LazyLock::new(|| {
         .and_then(parse_pixel_position_env_var)
 });
 
-actions!(assistant, [ShowConfiguration]);
-
 actions!(
     workspace,
     [