test(capital): strengthen GrantOffersApi test coverage for RequestOptions

The original getAllGrantOffers method had an overloaded version with no params which was
removed on latest updates, causing the compilation error in the CI pipeline. After fixing the
test, the two methods became identical. For this reason, this commit replaces the duplicate
testGetAllGrantOffersWithQueryParam (which was identical to testGetAllGrantOffers) with
testGetAllGrantOffersWithRequestOptions, verifying that idempotency keys are correctly
forwarded through the 2-arg overload of getAllGrantOffers.