Add upper pin for pandas and ignore pandas3/pyarrow deprecation warning

[ml-evs]

This PR ignores a new deprecation warning for pandas (sub-dep of pymatgen) and adds an upper pin for the case the message reflects (missing pyarrow). pandas v3 will therefore break pymatgen first so we shouldn't have to worry too much here.

Annoying gotcha: the emitted deprecation warning starts with a newline (took a while to notice this...) and filterwarnings only matches from the start of strings, so various obvious regex attempts fail and the newline needs to be explicitly added to the filter.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b646a0a) 90.75% compared to head (35a30d2) 90.75%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1945   +/-   ##
=======================================
  Coverage   90.75%   90.75%           
=======================================
  Files          75       75           
  Lines        4729     4729           
=======================================
  Hits         4292     4292           
  Misses        437      437           

Flag	Coverage Δ
project	90.75% <ø> (ø)
validator	90.67% <ø> (ø)

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