software/caddy-frontend/test: repair test

"bin/pythonwitheggs" no longer exist

See merge request !738
2 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.SlapRunner.ResilienceTest-Master

08:24:13

passed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

02:16:21