chore: change the value of all feature switches to `enable` in examples

examples/dashboard-with-https.conf.example

@@ -51,9 +51,6 @@ dashboard {
         ## Enable or disable peer verification
         verify = verify_none  ## use verify_peer to enable
 
-        ## if `verify' is ebabled, whit true, the connection fails if the client does not have a certificate to send
-        fail_if_no_peer_cert = false
-
         ## Enable TLS session reuse
         reuse_sessions = true
 

examples/prometheus.conf.example

@@ -23,6 +23,6 @@ prometheus {
     ## - ${host}: Host name of EMQX node
     job_name = "${name}/instance/${name}~${host}"
 
-    ## set true to enable this
-    enable = false
+    ## set to false to enable this
+    enable = true
 }

examples/psk_authentication.conf.example

@@ -7,8 +7,8 @@
 ##       you should copy and paste the below data into the emqx.conf for working
 
 psk_authentication {
-    ## set true to enable TLS PSK support
-    enable = false
+    ## set to false to disable
+    enable = true
 
     ## If init_file is specified, EMQX will import PSKs from the file into the built-in database at startup for use by the runtime
     init_file = "psk"