json: update the example in the module's README.md (#19544)

vlib/json/README.md

@@ -26,7 +26,7 @@ fn main() {
 	//
 	s := json.encode(x)
 	println('Employee x: ${s}')
-	assert s == '{"name":"Peter","age":28,"salary":95000.5,"title":2}'
+	assert s == '{"name":"Peter","age":28,"salary":95000.5,"title":"worker"}'
 	//
 	y := json.decode(Employee, s)!
 	//