Update docs for clone overlap

[zktuong]

• now colorby is optional. Default will always match groupby.
• added clarity to the docstring on how to use colorby to color sub-categories.
• remove unnecessary arguments in tl.clone_overlap and pl.clone_overlap.

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[codecov]

Codecov Report

Merging #276 (ef62b54) into master (8a50b91) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #276   +/-   ##
=======================================
  Coverage   82.24%   82.24%           
=======================================
  Files          47       47           
  Lines        9064     9064           
=======================================
  Hits         7455     7455           
  Misses       1609     1609           

Flag	Coverage Δ
unittests	82.24% <100.00%> (ø)

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Impacted Files	Coverage Δ
dandelion/tools/_tools.py	86.07% <ø> (ø)
dandelion/plotting/_plotting.py	82.78% <100.00%> (ø)
tests/test_mouse_plotting.py	100.00% <100.00%> (ø)