updating environment yaml

[atravitz]

removing openff-models since we vendored here, plus updating some other pins.

Also pinning us to a specific example notebooks release to resolve #1296

Checklist

• Added a news entry

Developers certificate of origin

• I certify that this contribution is covered by the MIT License here and the Developer Certificate of Origin at https://developercertificate.org/.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.47%. Comparing base (d33975c) to head (32ee528).
⚠️ Report is 228 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1385      +/-   ##
==========================================
- Coverage   94.63%   92.47%   -2.17%     
==========================================
  Files         143      143              
  Lines       10962    10962              
==========================================
- Hits        10374    10137     -237     
- Misses        588      825     +237     

Flag	Coverage Δ
fast-tests	92.47% <ø> (?)
slow-tests	?

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[IAlibay]

don't have strong views on OpenMM pin

[github-actions]

No API break detected ✅