fix: partial return on POS invoice (backport #43253)

[mergify]

version 15 and 14

fixes: #37998 & https://discuss.frappe.io/t/cant-submit-a-partial-return-on-pos-invoice/133331?u=ncp

Before:

before_pos_return.mp4

After:

after_pos_return.mp4

---

This is an automatic backport of pull request #43253 done by Mergify.

[mergify]

Cherry-pick of 76289fa has failed:

On branch mergify/bp/version-14-hotfix/pr-43253
Your branch is up to date with 'origin/version-14-hotfix'.

You are currently cherry-picking commit 76289fa8dc.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/accounts/doctype/pos_invoice/pos_invoice.py

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 18bdd06 has failed:

On branch mergify/bp/version-14-hotfix/pr-43253
Your branch is ahead of 'origin/version-14-hotfix' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 18bdd06652.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/accounts/doctype/pos_invoice/pos_invoice.py

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[frappe-pr-bot]

🎉 This PR is included in version 14.74.2 🎉

The release is available on GitHub release

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