### 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 (!list_type.is_hard_type()) {
			mark_node_unsafe(p_for->list);
		}
		if (list_type.is_variant()) {
			variable_type.kind = GDScriptParser::DataType::VARIANT;
			mark_node_unsafe(p_for->list);
		} else if (list_type.has_container_element_type()) {
			variable_type = list_type.get_container_element_type();
			variable_type.type_source = list_type.type_source;
		} else if (list_type.is_typed_container_type()) {
			variable_type = list_type.get_typed_container_type();
			variable_type.type_source = list_type.type_source;
		} else if (list_type.builtin_type == Variant::INT || list_type.builtin_type == Variant::FLOAT || list_type.builtin_type == Variant::STRING) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = list_type.builtin_type;
		} else if (list_type.builtin_type == Variant::VECTOR2I || list_type.builtin_type == Variant::VECTOR3I) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = Variant::INT;
		} else if (list_type.builtin_type == Variant::VECTOR2 || list_type.builtin_type == Variant::VECTOR3) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = Variant::FLOAT;
		} else if (list_type.builtin_type == Variant::OBJECT) {
			GDScriptParser::DataType return_type;
			List<GDScriptParser::DataType> par_types;
			int default_arg_count = 0;
			BitField<MethodFlags> method_flags;
			if (get_function_signature(p_for->list, false, list_type, CoreStringNames::get_singleton()->_iter_get, return_type, par_types, default_arg_count, method_flags)) {