[8.0.0] Outdated information on /about page

[tgurr]

Expected behavior

About page showing:

• Version 8.0.0
• Link to GMP documentation leading to: https://docs.greenbone.net/API/GMP/gmp-8.0.html

Actual behavior

About page showing:

• Version 8.0+beta2
• Link to GMP documentation leading to: https://docs.greenbone.net/API/GMP/gmp-7.0.html

Steps to reproduce

1. Navigate to https://gsa-instance.domain.local/about