### 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
consume(GDScriptTokenizer::Token::NEWLINE, R"(Expected a newline after "match" statement.)");
	if (!consume(GDScriptTokenizer::Token::INDENT, R"(Expected an indented block after "match" statement.)")) {
		complete_extents(match);
		return match;
	}
	bool all_have_return = true;
	bool have_wildcard = false;
	while (!check(GDScriptTokenizer::Token::DEDENT) && !is_at_end()) {
		MatchBranchNode *branch = parse_match_branch();
		if (branch == nullptr) {
			advance();
			continue;
		}
#ifdef DEBUG_ENABLED
		if (have_wildcard && !branch->patterns.is_empty()) {
			push_warning(branch->patterns[0], GDScriptWarning::UNREACHABLE_PATTERN);
		}
#endif
		have_wildcard = have_wildcard || branch->has_wildcard;
		all_have_return = all_have_return && branch->block->has_return;
		match->branches.push_back(branch);
	}
	complete_extents(match);
	consume(GDScriptTokenizer::Token::DEDENT, R"(Expected an indented block after "match" statement.)");
	if (all_have_return && have_wildcard) {
		current_suite->has_return = true;
	}
	return match;
}
GDScriptParser::MatchBranchNode *GDScriptParser::parse_match_branch() {