Count fragment function counts duplicates

[lauradmartens]

Describe the bug
The muon.atac.tl.count_fragments_features function uses the score in the fragment file to count fragments:

muon/muon/_atac/tools.py

Line 860 in 31a45d7

mx.data[i].append(int(fr.score)) # number of cuts per fragment (e.g. 2)

This score also includes all duplicated read pairs: https://support.10xgenomics.com/single-cell-atac/software/pipelines/latest/output/fragments, but we only want to use the unique fragments for downstream analysis and not the duplicates.

Expected behaviour
Only count the unique fragments by having:
mx.data[i].append(int(1))