all: replace generic <> with [] - part 2 (#16536)

vlib/json/json_decode_with_generic_test.v

@@ -1,6 +1,6 @@
 import json
 
-struct Result<T> {
+struct Result[T] {
 	ok     bool
 	result T
 }
@@ -10,14 +10,14 @@ struct User {
 	username string
 }
 
-fn func<T>() !T {
+fn func[T]() !T {
 	text := '{"ok": true, "result":{"id":37467243, "username": "ciao"}}'
-	a := json.decode(Result<T>, text)!
+	a := json.decode(Result[T], text)!
 	return a.result
 }
 
 fn test_decode_with_generic_struct() {
-	ret := func<User>()!
+	ret := func[User]()!
 	println(ret)
 	assert ret.id == 37467243
 	assert ret.username == 'ciao'