fix: set correct work experience during gratuity calculation (copy #2460)

[mergify]

Fix work experience calculation for gratuity rules using the Take Exact Completed Years method. Previously, the experience was rounded to a whole number instead of using the exact decimal value (eg. 1.4 years was incorrectly treated as 1 year).

Gratuity Rule:

Before:

After:

---

This is an automatic copy of pull request #2460 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of ce75e4e has failed:

On branch mergify/copy/version-14-hotfix/pr-2460
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 ce75e4e9.
  (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)

Changes to be committed:
	modified:   hrms/payroll/doctype/gratuity/gratuity.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   hrms/payroll/doctype/gratuity/gratuity.json

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 14.35.4 🎉

The release is available on GitHub release

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