fix: sim export_unittest for windows (#655)

## Description
Fix unittest of simulation export for windows systems

## Issue linked


## Checklist
- [x] I have tested my changes locally.
- [x] I have added necessary documentation or updated existing
documentation.
- [x] I have followed the coding style guidelines of this project.
- [x] I have added appropriate tests (unit, integration, system).
- [x] I have reviewed my changes before submitting this pull request.
- [x] I have linked the issue or issues that are solved by the PR if
any.
- [x] I have assigned this PR to myself.
- [x] I have made sure that the title of my PR follows [Conventional
commits style](https://www.conventionalcommits.org/en/v1.0.0/#summary)
(e.g. ``feat: add optical property``)
- [x] I have agreed with the Contributor License Agreement
([CLA](https://developer.ansys.com/form/cla-acceptance)).

---------

Co-authored-by: pyansys-ci-bot <[email protected]>
Co-authored-by: Pengyuan LU <[email protected]>

Author: 3 people

doc/changelog.d/655.fixed.md

@@ -0,0 +1 @@
+Sim export_unittest for windows

tests/helper.py

@@ -128,6 +128,15 @@ def remove_file(path):
     ----------
     path (str) - path of the file.
     """
+
+    def rmtree(f: Path):
+        if f.is_file():
+            f.unlink()
+        else:
+            for child in f.iterdir():
+                rmtree(child)
+            f.rmdir()
+
     if config.get("SpeosServerOnDocker"):
         subprocess.call(
             "docker exec "
@@ -138,4 +147,4 @@ def remove_file(path):
             shell=True,
         )
     else:
-        Path(path).unlink()
+        rmtree(Path(path))