minor #33211 [Routing] Remove orphaned TestObjectRouteLoader fixture …

…(derrabus)

This PR was merged into the 5.0-dev branch.

Discussion
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[Routing] Remove orphaned TestObjectRouteLoader fixture

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

This PR removes a fixture that was used by tests that have been removed by #32697.

Commits
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9f76c5d Remove orphaned TestObjectRouteLoader fixture.