When opening Geometry Nodes regression test files I always find a bit annoying that the `expected_object` and not the `test_object` is active. That's because only the `test_object` contains the modifier or node tree that is being tested. Therefore, usually my first step when opening these files is to select the `test_object` first. This patch changes it so that when mesh tests are updated, the `test_object` is made active in the end before the file is saved again. Pull Request: https://projects.blender.org/blender/blender/pulls/139088