test: remove eslint-disable for no-unused-expressions (#3349)

* test: remove eslint disable comment in middlewareTypes test

Remove ESLint disable comment and use void operator for intentional
unused expressions in type checking tests.

- Removed: /* eslint @typescript-eslint/no-unused-expressions: off */
- Added: void operator to all test expressions
- All tests pass with no ESLint errors

* test: use void only for value/property access in middlewareTypes test

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Co-authored-by: Daishi Kato <dai-shi@users.noreply.github.com>