Add disk write latency req for EC (#2885)

Author: paigecalvert

docs/partials/embedded-cluster/_requirements.mdx

@@ -6,6 +6,8 @@
 
 * At least 2GB of memory and 2 CPU cores
 
+* The disk on the host must have a maximum P99 write latency of 10 ms. This supports etcd performance and stability. For more information about the disk write latency requirements for etcd, see [Disks](https://etcd.io/docs/latest/op-guide/hardware/#disks) in _Hardware recommendations_ in the etcd documentation.
+
 * The filesystem at `/var/lib/embedded-cluster` has 40Gi or more of total space and must be less than 80% full
 
    :::note