Set explicit mode in zopen to address monty FutureWarning

[rkingsbury]

Explicitly sets mode='r' in zopen to avoid the following:

/home/ryan/miniforge3/envs/feynman/lib/python3.12/site-packages/maggma/stores/mongolike.py:712: FutureWarning: We strongly discourage using a default `mode`, it would beset to `r` now but would not be allowed after 2025-06-01
  with zopen(path) as f:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.91%. Comparing base (4ed05b8) to head (2d6fbb2).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1021   +/-   ##
=======================================
  Coverage   88.91%   88.91%           
=======================================
  Files          46       46           
  Lines        3997     3997           
=======================================
  Hits         3554     3554           
  Misses        443      443           

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