### 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 (base_type.kind != GDScriptParser::DataType::SCRIPT && base_type.kind != GDScriptParser::DataType::CLASS) { 
			push_error("Cannot assign a new value to a constant.", p_assignment->assignee);
			return;
		}
	} else if (assignee_type.is_read_only) {
		push_error("Cannot assign a new value to a read-only property.", p_assignment->assignee);
		return;
	} else if (p_assignment->assignee->type == GDScriptParser::Node::SUBSCRIPT) {
		GDScriptParser::SubscriptNode *sub = static_cast<GDScriptParser::SubscriptNode *>(p_assignment->assignee);
		while (sub) {
			const GDScriptParser::DataType &base_type = sub->base->datatype;
			if (base_type.is_hard_type() && base_type.is_read_only) {
				if (base_type.kind == GDScriptParser::DataType::BUILTIN && !Variant::is_type_shared(base_type.builtin_type)) {
					push_error("Cannot assign a new value to a read-only property.", p_assignment->assignee);
					return;
				}
			} else {
				break;
			}
			if (sub->base->type == GDScriptParser::Node::SUBSCRIPT) {
				sub = static_cast<GDScriptParser::SubscriptNode *>(sub->base);
			} else {
				sub = nullptr;
			}
		}
	}
	
	if (p_assignment->assigned_value->type == GDScriptParser::Node::ARRAY && assignee_type.has_container_element_type()) {
		update_array_literal_element_type(static_cast<GDScriptParser::ArrayNode *>(p_assignment->assigned_value), assignee_type.get_container_element_type());
	}