Standardize observation process equation notation between READMEs and tutorials.

[cdc-mitzimorris]

see issue #704

This PR updates the tutorials for the observation processes. It updates the formulas in the markdown cells and doesn't change any of the code cells in the notebooks or in the PyRenew package.

[cdc-mitzimorris]

@dylanhmorris @damonbayer - trivial PR, signoff appreciated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.91%. Comparing base (923fda8) to head (4a23091).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #715   +/-   ##
=======================================
  Coverage   97.91%   97.91%           
=======================================
  Files          51       51           
  Lines        1580     1580           
=======================================
  Hits         1547     1547           
  Misses         33       33           

Flag	Coverage Δ
unittests	97.91% <ø> (ø)

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[github-actions]

Thank you for your contribution @dylanhmorris 🚀! Your github-pages is ready for download 👉 here 👈!
_{(The artifact expires on 2026-03-02T22:59:58Z. You can re-generate it by re-running the workflow here.)}

[dylanhmorris]

Thanks @cdc-mitzimorris!