Fix XOR hamming distance calculation

[mchernys]

No description provided.

[mashu]

Fixed by using mismatches from BioSequences

"""
    compute_distance(metric::DistanceMetric, x::LongDNA{4}, y::LongDNA{4})::Float32

Compute the distance between two `LongDNA{4}` sequences using the specified distance metric.
"""
function compute_distance(::NormalizedHammingDistance, x::LongDNA{4}, y::LongDNA{4})::Float32
    @assert length(x) == length(y)
    return mismatches(x, y) / length(x)
end

For the

x = LongDNA{4}(rand("ATGC",30))
y = LongDNA{4}(rand("ATGC",30))
@btime compute_distance_old($x, $y) # gave 91.649ns (6 allocations: 288 bytes)
@btime compute_distance_old($x, $y) # gave 4.125ns (0 allocations: 0 bytes)

This is therefore closed by 52b3783

[mashu]

Closed by 52b3783