Expands the /opt/splunk size for splunk indexers

Systems are filling up current drives.
I'll manually update the existing ones instead of rebuilding them, but
this change will update teh ASG template.

prod/aws-us-gov/mdr-prod-nga/account.hcl

@@ -68,7 +68,7 @@ locals {
       "/var/log": 8, # minimum: 8
       "/var/log/audit": 8, # minimum: 8
       "/tmp": 4,  # minimum: 4
-      "/opt/splunk": 30, # No minimum; not in base image
+      "/opt/splunk": 60, # No minimum; not in base image
     },
     "searchhead" = {
       "swap": 8,  # minimum: 8