### 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
push_text("Match ");
	print_expression(p_match->test);
	push_line(" :");
	increase_indent();
	for (int i = 0; i < p_match->branches.size(); i++) {
		print_match_branch(p_match->branches[i]);
	}
	decrease_indent();
}
void GDScriptParser::TreePrinter::print_match_branch(MatchBranchNode *p_match_branch) {