fix: properly diff when using legacy UI with `toRender` matcher

[FrederikBolding]

This fixes two problems with diff outputs when using toRender with legacy UI:

• Firstly we had flipped actual and expected causing confusing output
• Secondly we were diffing not just the content but also the rest of the response object unnecessarily

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.30%. Comparing base (5e6db9d) to head (3ecb733).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2432 +/- ## ======================================= Coverage 94.30% 94.30% ======================================= Files 437 437 Lines 8987 8987 Branches 1378 1378 ======================================= Hits 8475 8475 Misses 512 512 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.