refactor universal: drop obsolete and inconsistent memory_order parameters in RateCounter

[ddvamp]

userver/universal/include/userver/utils/statistics/rate_counter.hpp

Line 48 in 5bcfaae

void Store(Rate desired, std::memory_order order = std::memory_order_relaxed) noexcept {

userver/universal/include/userver/utils/statistics/rate_counter.hpp

Line 54 in 5bcfaae

void Add(Rate arg, std::memory_order order = std::memory_order_relaxed) noexcept {

These parameters were added in this commit, and then turned out to be unnecessary in this one.

Since they are no longer in use and their presence contradicts the class description, they should be deleted.

[apolukhin]

I do not think it is worth removing. We may need it one day

It is better to adjust the class description with with relaxed memory ordering by default

[apolukhin]

^