MRG: Make print_dir_tree expand ~

[hoechenberger]

Merge checklist

Maintainer, please confirm the following before merging:

• All comments resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• PR description includes phrase "closes <#issue-number>"

[codecov]

Codecov Report

Merging #1013 (2beb12f) into main (2c1cdea) will decrease coverage by 1.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1013      +/-   ##
==========================================
- Coverage   95.17%   93.90%   -1.28%     
==========================================
  Files          25       25              
  Lines        3775     3774       -1     
==========================================
- Hits         3593     3544      -49     
- Misses        182      230      +48     

Impacted Files	Coverage Δ
mne_bids/path.py	97.67% <100.00%> (-0.01%)	⬇️
mne_bids/dig.py	88.85% <0.00%> (-9.76%)	⬇️
mne_bids/write.py	95.20% <0.00%> (-1.94%)	⬇️
mne_bids/utils.py	95.21% <0.00%> (-0.54%)	⬇️

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[agramfort]

Merge when green

[hoechenberger]

fNIRS-related CI failures seem to have nothing to do with this PR, merging