Use |to_json filter for serializing booleans to JSON

This should account for all cases where we were still doing such a thing.

Improvement suggested in #65 (Github issue).

roles/matrix-server/templates/corporal/config.json.j2

@@ -17,7 +17,7 @@
 	},
 
 	"HttpApi": {
-		"Enabled": {{ 'true' if matrix_corporal_http_api_enabled else 'false' }},
+		"Enabled": {{ matrix_corporal_http_api_enabled|to_json }},
 		"ListenAddress": "0.0.0.0:41081",
 		"AuthorizationBearerToken": "{{ matrix_corporal_http_api_auth_token }}"
 	},
@@ -25,6 +25,6 @@
 	"PolicyProvider": {{ matrix_corporal_policy_provider_config }},
 
 	"Misc": {
-		"Debug": {{ 'true' if matrix_corporal_debug else 'false' }}
+		"Debug": {{ matrix_corporal_debug|to_json }}
 	}
 }