Fix ahfe integration tests - missing restraints lamdas

[IAlibay]

Fix the tests for #735

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• Added a news entry

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 91.76%. Comparing base (bdde129) to head (d236e05).
Report is 1 commits behind head on main.

Files	Patch %	Lines
openfe/tests/protocols/test_openmm_afe_slow.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #750      +/-   ##
==========================================
- Coverage   91.77%   91.76%   -0.01%     
==========================================
  Files         133      133              
  Lines        9767     9768       +1     
==========================================
  Hits         8964     8964              
- Misses        803      804       +1     

Flag	Coverage Δ
fast-tests	91.76% <0.00%> (-0.01%)	⬇️

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