fix: unable to remove image from employee (backport #45793)

[mergify]

Current Premise

1. Employee image is "fetched from" user doctype, with "Fetch on save if empty" checked, but this only works on server side. For example create an employee attach an image to it, don't link user_id just yet. Create a user, don't attach any image to it. Now from system console, link the user to the employee. The image won't be overwritten.
2. "Fetch on save if empty" isn't meant to work client side, as soon as you set a value in a linked field, for example user_id, all fields of employee that depend on user, in this case image, should be updated regardless of if they are empty or not. This use-case explains why

The Problem

This, because the user is created after employee

Screen.Recording.2025-02-07.at.6.11.41.PM.mov

After

Screen.Recording.2025-02-07.at.6.36.08.PM.mov

Removing fetch from also solves the problem of not being able to remove image from employee, because it would be refetched as soon as it was removed.

---

This is an automatic backport of pull request #45793 done by Mergify.

[mergify]

Cherry-pick of 0207d2d has failed:

On branch mergify/bp/version-15-hotfix/pr-45793
Your branch is up to date with 'origin/version-15-hotfix'.

You are currently cherry-picking commit 0207d2d7b6.
  (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:   erpnext/setup/doctype/employee/employee.py

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