Revert "[Etherpad] Disable backups of pad.picasoft.net"

This reverts commit 21c1e819.

pica-db-backup/config/backup_config.json

@@ -10,6 +10,18 @@
     "Cron": "0 * * * *",
     "Init-Backup": "1"
   },
+  "etherpad": {
+    "Host": "etherpad-db",
+    "Port": "3306",
+    "User": "ETHERPAD_DB_USER",
+    "Password": "ETHERPAD_DB_PASSWORD",
+    "Database": "--all-databases",
+    "Type": "mysql",
+    "Folder": "etherpad",
+    "Cron": "0 */6 * * *",
+    "Options": "--single-transaction",
+    "Init-Backup": "1"
+  },
   "wekan": {
     "Host": "wekan-db",
     "Port": "27017",