Rename config variable "insecure_skip_verify" to "skip_verify". (#128)

Co-authored-by: Matheus C.R <matheus.carvalho@canonical.com>

config.yaml

@@ -106,9 +106,9 @@ options:
         For ssl/tls communication these should be a base64 encoded file
         e.g.:  "ca_file": "'"$(base64 -w 0 < my.custom.registry.pem)"'"
 
-      insecure_skip_verify: OPTIONAL bool - default false
+      skip_verify: OPTIONAL bool - default false
         For situatations where the registry has self-signed or expired certs and a quick work-around is necessary.
-        e.g.: "insecure_skip_verify": true
+        e.g.: "skip_verify": true
 
       example config)
       juju config containerd custom_registries='[{