ci: skipping wheel building for Linux 32-bit

[deepcharles]

As @oboulant explained here, cibuildwheel stopped working recently for some 32 bits setups (see also scikit-learn/scikit-learn#22122).

In this PR, wheels for cp38-manylinux_i686 and cp39-manylinux_i686 are explicitly excluded when uploading to PyPI, as well as the new musllinux supported by cibuildwheel (for now).

[codecov]

Codecov Report

Merging #227 (7666619) into master (2aea6b4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #227   +/-   ##
=======================================
  Coverage   98.77%   98.77%           
=======================================
  Files          40       40           
  Lines         978      978           
=======================================
  Hits          966      966           
  Misses         12       12           

Flag	Coverage Δ
unittests	98.77% <ø> (ø)

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