BIDSPath no longer warns on missing file

[sappelhoff]

PR Description

• closes No RuntimeWarning in the BIDSPath example although it is mentioned in the text #1178

Merge checklist

Maintainer, please confirm the following before merging.
If applicable:

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

[codecov]

Codecov Report

Merging #1181 (b5d4c3b) into main (e7fc975) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1181   +/-   ##
=======================================
  Coverage   97.63%   97.63%           
=======================================
  Files          40       40           
  Lines        8661     8661           
=======================================
  Hits         8456     8456           
  Misses        205      205