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.

editor/plugins/node_3d_editor_plugin.cpp

@@ -3254,14 +3254,12 @@ void Node3DEditorViewport::_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", callable_mp(this, &Node3DEditorViewport::_preview_exited_scene));
 		RS::get_singleton()->viewport_attach_camera(viewport->get_viewport_rid(), preview->get_camera()); //replace
-		view_menu->set_disabled(true);
 		surface->update();
 	}
 }
@@ -3508,7 +3506,6 @@ void Node3DEditorViewport::set_state(const Dictionary &p_state) {
 			previewing = Object::cast_to<Camera3D>(pv);
 			previewing->connect("tree_exiting", callable_mp(this, &Node3DEditorViewport::_preview_exited_scene));
 			RS::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();