Escape the \ in a docstring

[yarikoptic]

Otherwise lead to the warning

change is so minor that I do not think it is worth a changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (08315c1) 91.16% compared to head (29870db) 91.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##            maint    #7552      +/-   ##
==========================================
+ Coverage   91.16%   91.23%   +0.07%     
==========================================
  Files         325      325              
  Lines       43440    43440              
  Branches     5785     5785              
==========================================
+ Hits        39600    39634      +34     
+ Misses       3825     3791      -34     
  Partials       15       15              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[yarikoptic]

FTR Mac fail is

FAILED ../tests/test_annexrepo.py::test_is_available[False] - datalad.runner.exception.CommandError: CommandError: 'git -c diff.ignoreSubmodules=none -c core.quotepath=false annex find --anything --json --json-error-messages -c annex.dotfiles=true -- test-annex.dat' failed with exitcode 139 under /private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/datalad_temp_test_is_available7vgluc6z [info keys: stdout_json] [err: 'error: git-annex died of signal 11']