Update Borg Backups dashboard

Change storage box size from 10000 to 10240 GiB.

roles/grafana/files/dashboards/backups.json

@@ -99,7 +99,7 @@
       "targets": [
         {
           "exemplar": true,
-          "expr": "10000*2^30",
+          "expr": "10240*2^30",
           "interval": "",
           "legendFormat": "Quota",
           "queryType": "randomWalk",
@@ -115,7 +115,7 @@
         },
         {
           "exemplar": true,
-          "expr": "10000*2^30 - hetzner_storage_box_size_bytes{instance=\"monitoring.archlinux.org\"}",
+          "expr": "10240*2^30 - hetzner_storage_box_size_bytes{instance=\"monitoring.archlinux.org\"}",
           "hide": false,
           "interval": "",
           "legendFormat": "Snapshots",
@@ -123,7 +123,7 @@
         },
         {
           "exemplar": true,
-          "expr": "10000*2^30 - hetzner_storage_box_free_bytes{instance=\"monitoring.archlinux.org\"}",
+          "expr": "10240*2^30 - hetzner_storage_box_free_bytes{instance=\"monitoring.archlinux.org\"}",
           "hide": false,
           "interval": "",
           "legendFormat": "Total Used",