### 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
return parse_variable(p_is_static, true);
}
GDScriptParser::VariableNode *GDScriptParser::parse_variable(bool p_is_static, bool p_allow_property) {
	VariableNode *variable = alloc_node<VariableNode>();
	if (!consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected variable name after "var".)")) {
		complete_extents(variable);
		return nullptr;
	}
	variable->identifier = parse_identifier();
	variable->export_info.name = variable->identifier->name;
	variable->is_static = p_is_static;
	if (match(GDScriptTokenizer::Token::COLON)) {
		if (check(GDScriptTokenizer::Token::NEWLINE)) {
			if (p_allow_property) {
				advance();
				return parse_property(variable, true);
			} else {
				push_error(R"(Expected type after ":")");
				complete_extents(variable);
				return nullptr;
			}
		} else if (check((GDScriptTokenizer::Token::EQUAL))) {
			
			variable->infer_datatype = true;
		} else {
			if (p_allow_property) {
				make_completion_context(COMPLETION_PROPERTY_DECLARATION_OR_TYPE, variable);
				if (check(GDScriptTokenizer::Token::IDENTIFIER)) {