software/erp5: remove version pin on Jinja2

It's better for us to use a recent jinja2 version because we use it in
buildout profiles through slapos.recipe.template:jinja2
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-Jerome-WIP

19:02:39

failed SlapOS.SoftwareReleases.IntegrationTest-Jerome-WIP

08:26:08