### 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 (!class_exists(base_native)) {
			push_error(vformat("Native class %s used in script doesn't exist or isn't exposed.", base_native), p_source);
			return false;
		} else if (p_is_constructor && !ClassDB::can_instantiate(base_native)) {
			if (p_base_type.kind == GDScriptParser::DataType::CLASS) {
				push_error(vformat(R"(Class "%s" cannot be constructed as it is based on abstract native class "%s".)", p_base_type.class_type->fqcn.get_file(), base_native), p_source);
			} else if (p_base_type.kind == GDScriptParser::DataType::SCRIPT) {
				push_error(vformat(R"(Script "%s" cannot be constructed as it is based on abstract native class "%s".)", p_base_type.script_path.get_file(), base_native), p_source);
			} else {
				push_error(vformat(R"(Native class "%s" cannot be constructed as it is abstract.)", base_native), p_source);
			}
			return false;
		}
	}
	if (p_is_constructor) {
		function_name = GDScriptLanguage::get_singleton()->strings._init;
		r_method_flags.set_flag(METHOD_FLAG_STATIC);
	}
	GDScriptParser::ClassNode *base_class = p_base_type.class_type;
	GDScriptParser::FunctionNode *found_function = nullptr;
	while (found_function == nullptr && base_class != nullptr) {
		if (base_class->has_member(function_name)) {
			if (base_class->get_member(function_name).type != GDScriptParser::ClassNode::Member::FUNCTION) {
				
				push_error(vformat(R"(Member "%s" is not a function.)", function_name), p_source);
				return false;
			}
			resolve_class_member(base_class, function_name, p_source);