Fix #107294 : Node Editor "Frame All/Selected" ignore Smooth View

Caused by 3a1cf838ca.

Smooth view transitions only work when an operator is **invoked** (wont
work from **exec**, see `WM_operator_smooth_viewtx_get`).

Now 3a1cf838ca changed the `operator_context` for some other operators
in the menu to 'EXEC_REGION_WIN' (for good reason). But setting
`operator_context` on a `uiLayout` will set context on the **root**
layout (not the actual sublayout alone), so all following operators
"inherited" the [changed] context.

Now make sure following operators get properly invoked again by giving
the right context.

Pull Request: https://projects.blender.org/blender/blender/pulls/107296

scripts/startup/bl_ui/space_node.py

@@ -261,6 +261,7 @@ class NODE_MT_view(Menu):
 
         layout.separator()
 
+        layout.operator_context = 'INVOKE_REGION_WIN'
         layout.operator("node.view_selected")
         layout.operator("node.view_all")