### 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
for (int i = 0; i < 2; i++) {
		if (function->name == SNAME("set")) {
			if (setter_used) {
				push_error(R"(Properties can only have one setter.)");
			} else {
				parse_property_setter(property);
				setter_used = true;
			}
		} else if (function->name == SNAME("get")) {
			if (getter_used) {
				push_error(R"(Properties can only have one getter.)");
			} else {
				parse_property_getter(property);
				getter_used = true;
			}
		} else {
			
			push_error(R"(Expected "get" or "set" for property declaration.)");
		}
		if (i == 0 && p_variable->property == VariableNode::PROP_SETGET) {
			if (match(GDScriptTokenizer::Token::COMMA)) {
				
				if (match(GDScriptTokenizer::Token::NEWLINE)) {
					if (!p_need_indent) {
						push_error(R"(Inline setter/getter setting cannot span across multiple lines (use "\\"" if needed).)");
					}
				}
			} else {
				break;
			}