### 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_error(vformat(R"(Expected statement, found "%s" instead.)", previous.get_name()));
				}
			} else {
				end_statement("expression");
			}
			lambda_ended = lambda_ended || has_ended_lambda;
			result = expression;
#ifdef DEBUG_ENABLED
			if (expression != nullptr) {
				switch (expression->type) {
					case Node::CALL:
					case Node::ASSIGNMENT:
					case Node::AWAIT:
					case Node::TERNARY_OPERATOR:
						
						break;
					case Node::LAMBDA:
						
						push_error("Standalone lambdas cannot be accessed. Consider assigning it to a variable.", expression);
						break;
					case Node::LITERAL:
						if (static_cast<GDScriptParser::LiteralNode *>(expression)->value.get_type() == Variant::STRING) {
							
							break;
						}
						[[fallthrough]];
					default:
						push_warning(expression, GDScriptWarning::STANDALONE_EXPRESSION);
				}
			}