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.

codersdk/workspaceapps.go

@@ -38,13 +38,11 @@ type WorkspaceAppOpenIn string
 
 const (
 	WorkspaceAppOpenInSlimWindow WorkspaceAppOpenIn = "slim-window"
-	WorkspaceAppOpenInWindow     WorkspaceAppOpenIn = "window"
 	WorkspaceAppOpenInTab        WorkspaceAppOpenIn = "tab"
 )
 
 var MapWorkspaceAppOpenIns = map[WorkspaceAppOpenIn]struct{}{
 	WorkspaceAppOpenInSlimWindow: {},
-	WorkspaceAppOpenInWindow:     {},
 	WorkspaceAppOpenInTab:        {},
 }