chore: unused import warning in tests

[alrevuelta]

Background

Some tests like ./tests/v2/test_waku_filter.nim can't be run isolated without importing chronicles. If that import is removed, then the following fails. Note that this was fixed in #1375.

$ ./env.sh bash
$ nim c -r ./tests/v2/test_waku_filter.nim

However, after this fix, we get an UnusedImport warning when compiling all tests. This is clearly not the case, since as stated, if this import is removed the test can't be run isolated.

Acceptance criteria

UnusedImport is not shown anymore when compiling the tests make test2 but we still can run tests isolated.

[alrevuelta]

Check:

when defined(nimHasUsed): {.used.}

[vpavlin]

Is this still the case? I am not sure from the referenced PR