this change is a follow-up of 3129ae3c8c.
since in both cases in this change, the `num_ranges` should always
be greater than zero, there is no need to use `int` for its type,
and "num_ranges" returned by the CQL query should always be greater
or equal to zero, so there is no need to check if it is positive.
in this change, we
* change the type of `num_ranges` to `size_t`
* change std::cmp_not_equal() to !=
to avoid using the verbose `std::cmp_not_equal()` helper, for better
readability.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14754
8f390997cb