Previously, (presummably due to a typo) the `okToCacheOpaque` argument of `DataGroup#cacheResponse()` was essentially never taken into account (since opaque responses have a non-200 status code and thus `res.ok` is always false). This commit fixes the typo, which allows opaque responses to be cached when `okToCacheOpaque` is true (i.e. in data groups using the `freshness` strategy). Fixes #30968 PR Close #30977