### Godot version

v4.0.rc1.official [8843d9ad3]

### System information

Lubuntu

### Issue description

You can't use + or += to mutate typed arrays.

It seems to be not correctly getting the type information from the second operand.

An erudite poster on the discord puts it differently:
> it's more like operator + doesn't retain Array typing
> the syntax for Array Concatenation via operators, but the idea gets across i think


The error you see is:
```Trying to assign an array of type "Array" to a variable of type "Array[int]".```


### Steps to reproduce

```
	var Alice: Array[int] = [1,2,3]
	var Bob: Array[int] = [4,5,6]
	Alice += Bob
```
This will crash with the above error message.

### Minimal reproduction project

[plus_syntax_broken_demo_project.zip](https://github.com/godotengine/godot/files/10694514/plus_syntax_broken_demo_project.zip)

if (p_source == nullptr && parser->has_class(p_class)) {
		p_source = p_class;
	}
	if (p_class->resolved_body) {
		return;
	}
	if (!parser->has_class(p_class)) {
		String script_path = p_class->get_datatype().script_path;
		Ref<GDScriptParserRef> parser_ref = get_parser_for(script_path);
		if (parser_ref.is_null()) {
			push_error(vformat(R"(Could not find script "%s".)", script_path), p_source);
			return;
		}
		Error err = parser_ref->raise_status(GDScriptParserRef::PARSED);
		if (err) {
			push_error(vformat(R"(Could not resolve script "%s": %s.)", script_path, error_names[err]), p_source);
			return;
		}
		ERR_FAIL_COND_MSG(!parser_ref->get_parser()->has_class(p_class), R"(Parser bug: Mismatched external parser.)");
		GDScriptAnalyzer *other_analyzer = parser_ref->get_analyzer();
		GDScriptParser *other_parser = parser_ref->get_parser();
		int error_count = other_parser->errors.size();
		other_analyzer->resolve_class_body(p_class);
		if (other_parser->errors.size() > error_count) {
			push_error(vformat(R"(Could not resolve class "%s".)", p_class->fqcn), p_source);