Update redhat_subscriptions 'server_insecure' docs (#3373)

'server_insecure' maps to the subscription-manager config
(/etc/rhsm/rhsm.conf) value for 'insecure' key in the
'server' stanza. The 'insecure' configures if the https connection
to 'server_hostname' is verified as having been issued by
a CA in 'ca_cert_dir' trust store.

Previous documentation indicating it disables https and
enables http was inaccurate. Connection to server_hostname
always uses https.

packaging/os/redhat_subscription.py

@@ -36,7 +36,7 @@ options:
         default: Current value from C(/etc/rhsm/rhsm.conf) is the default
     server_insecure:
         description:
-            - Allow traffic over insecure http
+            - Enable or disable https server certificate verification when connecting to C(server_hostname)
         required: False
         default: Current value from C(/etc/rhsm/rhsm.conf) is the default
     rhsm_baseurl: