fix: opening bal double counting in Process Period Closing Voucher (backport #55495)

[mergify]

While closing period using the new controller (Process Period Closing Voucher), opening balances were being double counted.

---

This is an automatic backport of pull request #55495 done by Mergify.

[codecov]

Codecov Report

❌ Patch coverage is 98.68421% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 79.91%. Comparing base (cd7e1bb) to head (ce97a74).
⚠️ Report is 29 commits behind head on version-16.

Files with missing lines	Patch %	Lines
...ing_voucher/test_process_period_closing_voucher.py	98.66%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           version-16   #55502      +/-   ##
==============================================
+ Coverage       79.82%   79.91%   +0.08%     
==============================================
  Files            1172     1173       +1     
  Lines          127088   127164      +76     
==============================================
+ Hits           101451   101624     +173     
+ Misses          25637    25540      -97     

Files with missing lines	Coverage Δ
..._closing_voucher/process_period_closing_voucher.py	39.74% <100.00%> (+39.74%)	⬆️
...ing_voucher/test_process_period_closing_voucher.py	98.66% <98.66%> (ø)

... and 2 files with indirect coverage changes

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[frappe-pr-bot]

🎉 This PR is included in version 16.21.0 🎉

The release is available on GitHub release

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