Fix Backend error for vanilla

[MassBklf]

PlayStation added since Arma Reforger 1.2.1.169

Added PLATFORM_PSN to GAME_SUPPORTED_PLATFORMS in Dockerfile.

arma-reforger    |  BACKEND   (E): Vanilla community hosted servers must support all platforms or only PC!
arma-reforger    |  BACKEND   (E): Server Config file is Invalid - cannot start server!
arma-reforger    | BACKEND   (E): Unable to continue with a broken DS config! Shutdown!
arma-reforger    | ENGINE    (E): Error while initializing game.
arma-reforger    | ENGINE    (E): Unable to initialize the game
arma-reforger    | RESOURCES (E): ==== Resource leaks ====
arma-reforger    | RESOURCES (E): ui/fonts/robotomono_msdf_28.edds