Old assertions cr_assert/expect_arr_*_cmp are not documented properly

[interrupt-routine]

This is a regression of #269:
the old cr_assert/expect_arr_*_cmp assertions are incorrectly documented as taking the Size in bytes of the array in parameter instead of its length (count of elements).

Fixed here:
#551

I know that the old assertions will be deprecated/removed at some point, but at Codewars we are still using the old API and there are more than 1,500 C tests suites, which makes upgrading to the newer API really burdensome.