### 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
print_expression(p_test->operand);
	push_text(" IS ");
	print_type(p_test->test_type);
}
void GDScriptParser::TreePrinter::print_unary_op(UnaryOpNode *p_unary_op) {
	
	push_text("(");
	switch (p_unary_op->operation) {
		case UnaryOpNode::OP_POSITIVE:
			push_text("+");
			break;
		case UnaryOpNode::OP_NEGATIVE:
			push_text("-");
			break;
		case UnaryOpNode::OP_LOGIC_NOT:
			push_text("NOT");
			break;
		case UnaryOpNode::OP_COMPLEMENT:
			push_text("~");
			break;
	}
	print_expression(p_unary_op->operand);
	
	push_text(")");
}
void GDScriptParser::TreePrinter::print_variable(VariableNode *p_variable) {