### Godot version

4.0 stable

### System information

Fedora, RX 590

### Issue description

I made a dictionary, and instead of using `:` to separate between key and value, i accidentally used `=`.
The error message was not clear at all `Parse Error: Expected identifier or string as LUA-style dictionary key.` 

I don't think assuming that people know how dictionaries are made in LUA is reasonable. And if this is not about LUA the programming language, i don't even know what this is about :D

I think this error should be replaced with something of the sort "Please use `:` as separator instead of `=` in your dictionary"

### Steps to reproduce

Paste this code in a script:

```

var dict = {
	1 = "lala"
}
```

Observe the error message
![image](https://user-images.githubusercontent.com/7917475/224549538-38ea25aa-ba75-431e-868b-0733a53b90ad.png)


### Minimal reproduction project

see above
while (check(GDScriptTokenizer::Token::DEDENT) || check(GDScriptTokenizer::Token::INDENT) || check(GDScriptTokenizer::Token::NEWLINE)) {
			current = tokenizer.scan(); 
		}
		tokenizer.pop_expression_indented_block();
	}
	current_function = previous_function;
	in_lambda = previous_in_lambda;
	lambda->function = function;
	
	can_break = could_break;
	can_continue = could_continue;
	return lambda;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_type_test(ExpressionNode *p_previous_operand, bool p_can_assign) {
	TypeTestNode *type_test = alloc_node<TypeTestNode>();
	reset_extents(type_test, p_previous_operand);
	update_extents(type_test);
	type_test->operand = p_previous_operand;
	type_test->test_type = parse_type();
	complete_extents(type_test);
	if (type_test->test_type == nullptr) {
		push_error(R"(Expected type specifier after "is".)");
	}
	return type_test;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_yield(ExpressionNode *p_previous_operand, bool p_can_assign) {
	push_error(R"("yield" was removed in Godot 4.0. Use "await" instead.)");
	return nullptr;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_invalid_token(ExpressionNode *p_previous_operand, bool p_can_assign) {