Re-enable Flutter customer testing once `inspector_v2/inspector_integration_test.dart` is updated

[bkonyi]

screenshot tests expand and collapse implementation widgets in inspector_v2/inspector_integration_test.dart is blocking flutter/flutter#169229 from landing as it's using the number of widgets in the tree to find the correct button to select:

        // Expand the hidden group that contains the HeroControllerScope:
        final expandButton = findExpandCollapseButtonForNode(
          nodeDescription: '71 more widgets...', // This needs to be updated to 72
          isExpand: true,
        );

These tests ideally should be using keys to select specific nodes, but in the meantime, I'm going to disable DevTools customer testing until the above PR lands.

[kenzieschmoll]

@elliette

[elliette]

Note: We will need to re-enable the golden checks (disabled in #9226) and update the goldens once flutter/flutter#169229 lands and the Flutter candidate in DevTools has been updated.

[srawlins]

AFAICT these were re-enabled at some point.