[bugfix] Allow user to edit colormap for depth images (#3241)

### What
Resolves: #3240

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/3241) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/3241)
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crates/re_viewer/src/ui/selection_panel.rs

@@ -425,7 +425,7 @@ fn colormap_props_ui(ui: &mut egui::Ui, entity_props: &mut EntityProperties) {
                     .selectable_label(current == proposed, proposed.to_string())
                     .clicked()
                 {
-                    entity_props.color_mapper = EditableAutoValue::Auto(proposed);
+                    entity_props.color_mapper = EditableAutoValue::UserEdited(proposed);
                 }
             };