### 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(R"(Expected "func" or "var" after "static".)");
				}
			} break;
			case GDScriptTokenizer::Token::ANNOTATION: {
				advance();
				
				AnnotationNode *annotation = parse_annotation(AnnotationInfo::STANDALONE | AnnotationInfo::CLASS_LEVEL);
				if (annotation != nullptr) {
					if (annotation->applies_to(AnnotationInfo::STANDALONE)) {
						if (previous.type != GDScriptTokenizer::Token::NEWLINE) {
							push_error(R"(Expected newline after a standalone annotation.)");
						}
						if (annotation->name == SNAME("@export_category") || annotation->name == SNAME("@export_group") || annotation->name == SNAME("@export_subgroup")) {
							current_class->add_member_group(annotation);
						} else {
							
							push_error(R"(Unexpected standalone annotation in class body.)");
						}
					} else {
						annotation_stack.push_back(annotation);
					}
				}
				break;
			}
			case GDScriptTokenizer::Token::PASS:
				advance();
				end_statement(R"("pass")");
				break;
			case GDScriptTokenizer::Token::DEDENT:
				class_end = true;