Allow using the 3D editor's View menu while previewing a camera

This is already allowed when using cinematic preview, but not
when previewing a Camera3D the usual way.

Many operations from the View menu still work while previewing
a camera, such as switching between debug draw modes and toggling
information panes.

(cherry picked from commit fab3d136e0c1f3a3ba2a98dbc1f8cc1568858eee)

editor/plugins/spatial_editor_plugin.cpp

@@ -3076,14 +3076,12 @@ void SpatialEditorViewport::_toggle_camera_preview(bool p_activate) {
 		if (!preview) {
 			preview_camera->hide();
 		}
-		view_menu->set_disabled(false);
 		surface->update();
 
 	} else {
 		previewing = preview;
 		previewing->connect("tree_exiting", this, "_preview_exited_scene");
 		VS::get_singleton()->viewport_attach_camera(viewport->get_viewport_rid(), preview->get_camera()); //replace
-		view_menu->set_disabled(true);
 		surface->update();
 	}
 }
@@ -3316,7 +3314,6 @@ void SpatialEditorViewport::set_state(const Dictionary &p_state) {
 			previewing = Object::cast_to<Camera>(pv);
 			previewing->connect("tree_exiting", this, "_preview_exited_scene");
 			VS::get_singleton()->viewport_attach_camera(viewport->get_viewport_rid(), previewing->get_camera()); //replace
-			view_menu->set_disabled(true);
 			surface->update();
 			preview_camera->set_pressed(true);
 			preview_camera->show();