From https://en.wikipedia.org/wiki/NaN#Display, it says
that apart from nan and -nan, we can also get NAN and even
nan(char-sequence) from libc.
In #11482, our conclusion was that we wanna normalize it in
Redis to a single nan type, like we already normalized inf.
For this, we also reverted the assert_match part of the test
added in #11506, using assert_equal to validate the changes.
fa5474e153