CompatHelper: bump compat for ITensorMPS to 0.4 for package test, (keep existing compat)

[ITensorBot]

This pull request changes the compat entry for the ITensorMPS package from 0.3.6 to 0.3.6, 0.4 for package test.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.08%. Comparing base (a16b018) to head (4ee78fd).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #345      +/-   ##
==========================================
- Coverage   73.11%   73.08%   -0.04%     
==========================================
  Files          66       66              
  Lines        3151     3151              
==========================================
- Hits         2304     2303       -1     
- Misses        847      848       +1     

Flag	Coverage Δ
docs	46.63% <ø> (-0.04%)	⬇️

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[mtfishman]

Closing — ITensorMPS is on track to be dropped from test/Project.toml entirely as part of the legacy cleanup, so this compat bump won't be needed.