### 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
set_last_completion_call_arg(argument_index++);
			ExpressionNode *argument = parse_expression(false);
			if (argument == nullptr) {
				push_error("Expected expression as the annotation argument.");
				valid = false;
				continue;
			}
			annotation->arguments.push_back(argument);
		} while (match(GDScriptTokenizer::Token::COMMA) && !is_at_end());
		pop_multiline();
		consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, R"*(Expected ")" after annotation arguments.)*");
		pop_completion_call();
	}
	complete_extents(annotation);
	match(GDScriptTokenizer::Token::NEWLINE); 
	if (valid) {
		valid = validate_annotation_arguments(annotation);
	}
	return valid ? annotation : nullptr;
}
void GDScriptParser::clear_unused_annotations() {
	for (const AnnotationNode *annotation : annotation_stack) {
		push_error(vformat(R"(Annotation "%s" does not precede a valid target, so it will have no effect.)", annotation->name), annotation);
	}
	annotation_stack.clear();
}
bool GDScriptParser::register_annotation(const MethodInfo &p_info, uint32_t p_target_kinds, AnnotationAction p_apply, const Vector<Variant> &p_default_arguments, bool p_is_vararg) {
	ERR_FAIL_COND_V_MSG(valid_annotations.has(p_info.name), false, vformat(R"(Annotation "%s" already registered.)", p_info.name));
	AnnotationInfo new_annotation;
	new_annotation.info = p_info;