fix: add currency in options for rate field in pricing rule (backport #43239)

[mergify]

Issue:
Not showing appropriate currency symbol in rate field in pricing rule list view
https://support.frappe.io/helpdesk/tickets/22014

Before fix:

After fix:

Backport needed:
v15

---

This is an automatic backport of pull request #43239 done by Mergify.

[mergify]

Cherry-pick of 636c013 has failed:

On branch mergify/bp/version-14-hotfix/pr-43239
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Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/accounts/doctype/pricing_rule/pricing_rule.json

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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 14.74.1 🎉

The release is available on GitHub release

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