software/theia/test: adjust ERP5 test for testing-short-embedded-instance-path

We can not use the new theia parameter from 4bb65573 (software/theia: new
testing-short-embedded-instance-path parameter for tests, 2024-11-04),
because ERP5 Software release still uses some slapos.toolbox utility
hardcoding srv/runner/instance/slappart\d

https://lab.nexedi.com/nexedi/slapos.toolbox/-/blob/8fc29341d366f17544a56d7f6c8bd3716055a128/slapos/resilient/identity_script_excluding_path.py#L25

Instead, just keep using normal long paths, because they were not too
long for ERP5 in theia in testnode