### 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
AssertNode *assert = alloc_node<AssertNode>();
	push_multiline(true);
	consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected "(" after "assert".)");
	assert->condition = parse_expression(false);
	if (assert->condition == nullptr) {
		push_error("Expected expression to assert.");
		pop_multiline();
		complete_extents(assert);
		return nullptr;
	}
	if (match(GDScriptTokenizer::Token::COMMA) && !check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE)) {
		assert->message = parse_expression(false);
		if (assert->message == nullptr) {
			push_error(R"(Expected error message for assert after ",".)");
			pop_multiline();
			complete_extents(assert);
			return nullptr;
		}
		match(GDScriptTokenizer::Token::COMMA);
	}
	pop_multiline();
	consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, R"*(Expected ")" after assert expression.)*");
	complete_extents(assert);
	end_statement(R"("assert")");
	return assert;
}
GDScriptParser::BreakNode *GDScriptParser::parse_break() {