### 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
operation->variant_op = Variant::OP_GREATER;
			break;
		case GDScriptTokenizer::Token::GREATER_EQUAL:
			operation->operation = BinaryOpNode::OP_COMP_GREATER_EQUAL;
			operation->variant_op = Variant::OP_GREATER_EQUAL;
			break;
		default:
			return nullptr; 
	}
	return operation;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_ternary_operator(ExpressionNode *p_previous_operand, bool p_can_assign) {
	
	TernaryOpNode *operation = alloc_node<TernaryOpNode>();
	reset_extents(operation, p_previous_operand);
	update_extents(operation);
	operation->true_expr = p_previous_operand;
	operation->condition = parse_precedence(PREC_TERNARY, false);
	if (operation->condition == nullptr) {
		push_error(R"(Expected expression as ternary condition after "if".)");
	}
	consume(GDScriptTokenizer::Token::ELSE, R"(Expected "else" after ternary operator condition.)");
	operation->false_expr = parse_precedence(PREC_TERNARY, false);
	if (operation->false_expr == nullptr) {
		push_error(R"(Expected expression after "else".)");
	}
	complete_extents(operation);
	return operation;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_assignment(ExpressionNode *p_previous_operand, bool p_can_assign) {