### 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)

found_function = base_class->get_member(function_name).function;
		}
		resolve_class_inheritance(base_class, p_source);
		base_class = base_class->base_type.class_type;
	}
	if (found_function != nullptr) {
		if (p_is_constructor || found_function->is_static) {
			r_method_flags.set_flag(METHOD_FLAG_STATIC);
		}
		for (int i = 0; i < found_function->parameters.size(); i++) {
			r_par_types.push_back(found_function->parameters[i]->get_datatype());
			if (found_function->parameters[i]->initializer != nullptr) {
				r_default_arg_count++;
			}
		}
		r_return_type = p_is_constructor ? p_base_type : found_function->get_datatype();
		r_return_type.is_meta_type = false;
		r_return_type.is_coroutine = found_function->is_coroutine;
		return true;
	}
	Ref<Script> base_script = p_base_type.script_type;
	while (base_script.is_valid() && base_script->has_method(function_name)) {
		MethodInfo info = base_script->get_method_info(function_name);
		if (!(info == MethodInfo())) {
			return function_signature_from_info(info, r_return_type, r_par_types, r_default_arg_count, r_method_flags);
		}
		base_script = base_script->get_base_script();
	}
	
	if (p_base_type.is_meta_type && !p_is_constructor && (p_base_type.kind == GDScriptParser::DataType::SCRIPT || p_base_type.kind == GDScriptParser::DataType::CLASS)) {