Update shebang and date to POSIX format for working on FreeBSD (not

tested on Linux)

scripts/upgrade.sh

@@ -1,10 +1,10 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Strict mode
 set -e
 
 # Backup database
-SQL_BACKUP_PATH="/var/www/peertube/backup/sql-peertube_prod-$(date -Im).bak" 
+SQL_BACKUP_PATH="/var/www/peertube/backup/sql-peertube_prod-$(date +\"%Y%m%d-%h%m\").bak" 
 mkdir -p /var/www/peertube/backup
 pg_dump -U peertube -W -h localhost -F c peertube_prod -f "$SQL_BACKUP_PATH"