Increase the volume size (150->200GiB) for monitoring.al.org

With Loki needing roughly 108GiB[1] and Prometheus at least[2]
116GiB[3], 200GiB sounds like a good starting point.

[1] increase(loki_ingester_chunk_stored_bytes_total[1w]) / 7 * 90
[2] https://www.robustperception.io/how-much-disk-space-do-prometheus-blocks-use
[3] (rate(prometheus_tsdb_compaction_chunk_size_bytes_sum[1w]) /
    rate(prometheus_tsdb_compaction_chunk_samples_sum[1w])) *
    increase(prometheus_tsdb_head_samples_appended_total[1w]) / 7 * 365

tf-stage1/archlinux.tf

@@ -494,6 +494,6 @@ resource "hcloud_volume" "homedir" {
 
 resource "hcloud_volume" "monitoring" {
   name      = "monitoring"
-  size      = 150
+  size      = 200
   server_id = hcloud_server.machine["monitoring.archlinux.org"].id
 }