Update Gcore apikey format

I managed to mis-write the format in my previous commit

global/certbot-dns-plugins.json

@@ -212,7 +212,7 @@
 		"package_name": "certbot-dns-gcore",
 		"version": "~=0.1.8",
 		"dependencies": "",
-		"credentials": "dns_gcore_api_key = 0123456789abcdef0123456789abcdef01234567",
+		"credentials": "dns_gcore_apitoken = 0123456789abcdef0123456789abcdef01234567",
 		"full_plugin_name": "dns-gcore"
 	},
 	"godaddy": {