Removed trivial/redundant integration card_integration tests

#381 in iced-rs/iced_aw — merged 2025-12-28

After review, the integration tests I wrote in tests/card_integration_tests.rs had substantial overlap and many of them didn't actually verify behavior beyond "it renders without panicking." I cleaned them up.

# Integration tests
 cargo test --test card_integration_tests -- --test-threads=1