### 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)

is_self = true;
		if (p_call->callee == nullptr && !lambda_stack.is_empty()) {
			push_error("Cannot use `super()` inside a lambda.", p_call);
		}
	} else if (callee_type == GDScriptParser::Node::IDENTIFIER) {
		base_type = parser->current_class->get_datatype();
		base_type.is_meta_type = false;
		is_self = true;
	} else if (callee_type == GDScriptParser::Node::SUBSCRIPT) {
		GDScriptParser::SubscriptNode *subscript = static_cast<GDScriptParser::SubscriptNode *>(p_call->callee);
		if (subscript->base == nullptr) {
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		if (!subscript->is_attribute) {
			
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		if (subscript->attribute == nullptr) {
			
			p_call->set_datatype(call_type);
			mark_node_unsafe(p_call);
			return;
		}
		GDScriptParser::IdentifierNode *base_id = nullptr;