nixos/mediamtx: restart service on failure (#374588)

Co-authored-by: Masum Reza <[e-mail]>

nixos/modules/services/video/mediamtx.nix

···
         Group = "mediamtx";
         SupplementaryGroups = lib.mkIf cfg.allowVideoAccess "video";
         ExecStart = "${cfg.package}/bin/mediamtx /etc/mediamtx.yaml";
+        Restart = "on-failure";
       };
     };
   };