make sure installation works

[rndmh3ro]

Problem

before this fix, the installation could not complete because invoiceninja checks if an env-file exists. if it does, it complains and setup wont finish. this fix comments the code for this check.

• [x] Code finished and ready to be reviewed/tested
• [x] The fix/enhancement were manually tested (if applicable)

Automatic tests

Automatic tests can be triggered on https://ci-apps-dev.yunohost.org/ after creating the PR, by commenting "!testme", "!gogogadgetoci" or "By the power of systemd, I invoke The Great App CI to test this Pull Request!". (N.B. : for this to work you need to be a member of the Yunohost-Apps organization)

[rndmh3ro]

!testme

[yunohost-bot]

Meow :cat2: