Fix default CORS settings. (#7387)

* Fix default CORS settings.

* Add info regarding special options.

parity/cli/tests/config.full.toml

@@ -49,7 +49,7 @@ reserved_peers = "./path_to_file"
 disable = false
 port = 8545
 interface = "local"
-cors = "null"
+cors = ["null"]
 apis = ["web3", "eth", "net", "parity", "traces", "rpc", "secretstore"]
 hosts = ["none"]
 
@@ -76,7 +76,7 @@ path = "$HOME/.parity/dapps"
 user = "test_user"
 pass = "test_pass"
 
-[secretstore]	
+[secretstore]
 disable = false
 disable_http = false
 disable_acl_check = false
@@ -91,7 +91,7 @@ path = "$HOME/.parity/secretstore"
 enable = false
 port = 5001
 interface = "local"
-cors = "null"
+cors = ["null"]
 hosts = ["none"]
 
 [mining]