Remove Texas Medicaid deprivation requirement

[daphnehanse11]

Summary

• remove Texas from the Medicaid parent deprivation requirement parameter
• add regression coverage for a low-income joint-filing Texas household with two parents and one child
• add a changelog fragment for the fix

Why

Texas no longer enforces the deprivation requirement for the parent/caretaker Medicaid pathway, so keeping TX: true on main incorrectly blocks eligible two-parent households.

Fixes #7976.

Impact

This restores parent Medicaid eligibility in Texas for qualifying two-parent households instead of denying them through the single-parent deprivation proxy.

Validation

• make format
• /tmp/policyengine-us-issue-7976/.venv/bin/policyengine-core test policyengine_us/tests/policy/baseline/gov/hhs/medicaid/eligibility/categories/is_parent_for_medicaid.yaml -c policyengine_us -v
• direct simulation check for the 2025 Texas two-parent household from the reported issue scenario

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.37%. Comparing base (b70c547) to head (bf6ee3b).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##              main    #7977       +/-   ##
============================================
- Coverage   100.00%   71.37%   -28.63%     
============================================
  Files            1     4212     +4211     
  Lines           13    60818    +60805     
  Branches         0      307      +307     
============================================
+ Hits            13    43406    +43393     
- Misses           0    17405    +17405     
- Partials         0        7        +7     

Flag	Coverage Δ
unittests	71.37% <ø> (-28.63%)	⬇️

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