### 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
case GDScriptTokenizer::Token::NOT:
		case GDScriptTokenizer::Token::BANG:
			operation->operation = UnaryOpNode::OP_LOGIC_NOT;
			operation->variant_op = Variant::OP_NOT;
			operation->operand = parse_precedence(PREC_LOGIC_NOT, false);
			if (operation->operand == nullptr) {
				push_error(vformat(R"(Expected expression after "%s" operator.)", op_type == GDScriptTokenizer::Token::NOT ? "not" : "!"));
			}
			break;
		default:
			complete_extents(operation);
			return nullptr; 
	}
	complete_extents(operation);
	return operation;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_binary_not_in_operator(ExpressionNode *p_previous_operand, bool p_can_assign) {
	
	UnaryOpNode *operation = alloc_node<UnaryOpNode>();
	reset_extents(operation, p_previous_operand);
	update_extents(operation);
	consume(GDScriptTokenizer::Token::IN, R"(Expected "in" after "not" in content-test operator.)");
	ExpressionNode *in_operation = parse_binary_operator(p_previous_operand, p_can_assign);
	operation->operation = UnaryOpNode::OP_LOGIC_NOT;
	operation->variant_op = Variant::OP_NOT;
	operation->operand = in_operation;
	complete_extents(operation);
	return operation;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_binary_operator(ExpressionNode *p_previous_operand, bool p_can_assign) {