OCPBUGS-9295: Updated the --insecure flag desc. in installation docs

Author: dfitzmau

modules/installation-user-infra-machines-static-network.adoc

@@ -404,7 +404,7 @@ a|`--save-partindex <id>...`
 a|Save partitions with this number or range.
 
 a|`--insecure`
-a|Skip signature verification.
+a|Skip {op-system} image signature verification.
 
 a|`--insecure-ignition`
 a|Allow Ignition URL without HTTPS or hash.