Tool System: don't unlink tools when changing workspaces

Caused gizmos to be lost with multiple main windows whenever one of them
switched workspaces.

Rely on tool gizmos poll function to unlink to gizmo.

source/blender/editors/screen/workspace_edit.c

@@ -183,9 +183,6 @@ bool ED_workspace_change(WorkSpace *workspace_new, bContext *C, wmWindowManager
 
   BLI_assert(CTX_wm_workspace(C) == workspace_new);
 
-  WM_toolsystem_unlink_all(C, workspace_old);
-  /* Area initialization will initialize based on the new workspace. */
-
   /* Automatic mode switching. */
   if (workspace_new->object_mode != workspace_old->object_mode) {
     ED_object_mode_generic_enter(C, workspace_new->object_mode);