context: Fixed negated permission string for allow and share options

It was solved partially in e0e1b20, but not for completely disallowed code path.
Steps to reproduce:
1. Run any flatpak with explicit --unshare option, e.g:
    [user@user-standardpc ~]$ flatpak run --unshare=network --command=bash io.gitlab.librewolf-community
2. Inside flatpak shell spawn any executable:
    [io.gitlab.librewolf-community ~]$ flatpak-spawn ls /
Result is:
error: Unknown option --noshare=network
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