tests: Properly pass -y to install

This bug was unearthed when we suddenly started to fail when you
answered no to the prompt.

Closes: #2858
Approved by: alexlarsson
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f