### 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
if (path_state != PATH_STATE_START && path_state != PATH_STATE_SLASH) {
				push_error(R"("%" is only valid in the beginning of a node name (either after "$" or after "/"))");
				complete_extents(get_node);
				return nullptr;
			}
			get_node->full_path += "%";
			path_state = PATH_STATE_PERCENT;
		} else if (previous.type == GDScriptTokenizer::Token::SLASH) {
			if (path_state != PATH_STATE_START && path_state != PATH_STATE_NODE_NAME) {
				push_error(R"("/" is only valid at the beginning of the path or after a node name.)");
				complete_extents(get_node);
				return nullptr;
			}
			get_node->full_path += "/";
			path_state = PATH_STATE_SLASH;
		}
		make_completion_context(COMPLETION_GET_NODE, get_node, context_argument++);
		if (match(GDScriptTokenizer::Token::LITERAL)) {
			if (previous.literal.get_type() != Variant::STRING) {
				String previous_token;
				switch (path_state) {
					case PATH_STATE_START:
						previous_token = "$";
						break;
					case PATH_STATE_PERCENT:
						previous_token = "%";
						break;
					case PATH_STATE_SLASH:
						previous_token = "/";
						break;