chore(coderd): remove the window option in open_in (#16104)

As we worked on adding a `open_in` parameter for workspace_apps - we
initially created three options :
- window
- slim_window
- tab

After further investigation, `window` should not be used and has to be
removed.

ℹ️ I decided to remove the option instead of deprecating it as we've not
created any release nor documented the feature. Can be discussed.

docs/reference/api/schemas.md

@@ -7652,7 +7652,6 @@ If the schedule is empty, the user will be updated to use the default schedule.|
 | Value         |
 |---------------|
 | `slim-window` |
-| `window`      |
 | `tab`         |
 
 ## codersdk.WorkspaceAppSharingLevel