[ENH] turn off check in BaseObject.clone

[fkiraly]

This PR turns off the check in BaseObject.clone, which unintentionally couples clone to pytest, via import of deep_equals that imports pytest by accident (through __init__).

This can be done without deprecation, ahead of a refactor that moves deep_equals out of the testing module.

Fast fix for #177 but does not address it finally (if check_clone config is True, the bug still occurs)

[codecov-commenter]

Codecov Report

Merging #176 (a6e1772) into main (9a5c70c) will decrease coverage by 0.26%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main     #176      +/-   ##
==========================================
- Coverage   82.89%   82.64%   -0.26%     
==========================================
  Files          39       39              
  Lines        2777     2777              
==========================================
- Hits         2302     2295       -7     
- Misses        475      482       +7     

Impacted Files	Coverage Δ
skbase/base/_base.py	80.06% <ø> (ø)

... and 1 file with indirect coverage changes