### 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
ERR_FAIL_COND(p_source == nullptr);
	if (is_ignoring_warnings) {
		return;
	}
	if (GLOBAL_GET("debug/gdscript/warnings/exclude_addons").booleanize() && script_path.begins_with("res://addons/")) {
		return;
	}
	if (ignored_warnings.has(p_code)) {
		return;
	}
	int warn_level = (int)GLOBAL_GET(GDScriptWarning::get_settings_path_from_code(p_code));
	if (!warn_level) {
		return;
	}
	GDScriptWarning warning;
	warning.code = p_code;
	warning.symbols = p_symbols;
	warning.start_line = p_source->start_line;
	warning.end_line = p_source->end_line;
	warning.leftmost_column = p_source->leftmost_column;
	warning.rightmost_column = p_source->rightmost_column;
	if (warn_level == GDScriptWarning::WarnLevel::ERROR) {
		push_error(warning.get_message() + String(" (Warning treated as error.)"), p_source);
		return;
	}
	List<GDScriptWarning>::Element *before = nullptr;
	for (List<GDScriptWarning>::Element *E = warnings.front(); E; E = E->next()) {