Github CI test failed on case of test_eviction in pingora-memory-cache

## Describe the bug

Github CI test failed on case of test_eviction in pingora-memory-cache.
```
failures:

---- tests::test_eviction stdout ----
thread 'tests::test_eviction' panicked at 'assertion failed: `(left == right)`
left: `Some(2)`,
right: `None`', pingora-memory-cache/src/lib.rs:327:9

failures:
tests::test_eviction

test result: FAILED. 19 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 2.37s
```
https://github.com/cloudflare/pingora/actions/runs/14658961515/job/41139008443

## Pingora info

**Pingora version**: a1baa60d5ab39c35804f5b98f0b0322e6cf94535 (on pr https://github.com/cloudflare/pingora/pull/590/commits/7219a5df96f872a30a37e6bfa0d2df4da0ca4738)
**Rust version**: 1.72.0
**Operating system version**: github action container

## Steps to reproduce

https://github.com/cloudflare/pingora/actions/runs/14658961515/job/41139008443

## Expected results

CI should success

## Observed results

Test case of pingora-memory-cache failed

## Additional context