### 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)

GDScriptParser::IdentifierNode *identifier = nullptr;
	if (p_node->type == GDScriptParser::Node::IDENTIFIER) {
		identifier = static_cast<GDScriptParser::IdentifierNode *>(p_node);
	} else if (p_node->type == GDScriptParser::Node::SUBSCRIPT) {
		GDScriptParser::SubscriptNode *subscript = static_cast<GDScriptParser::SubscriptNode *>(p_node);
		if (subscript->is_attribute) {
			identifier = subscript->attribute;
		}
	}
	if (identifier == nullptr) {
		return;
	}
	GDScriptParser::Node *source = nullptr;
	switch (identifier->source) {
		case GDScriptParser::IdentifierNode::MEMBER_VARIABLE: {
			source = identifier->variable_source;
		} break;
		case GDScriptParser::IdentifierNode::FUNCTION_PARAMETER: {
			source = identifier->parameter_source;
		} break;
		case GDScriptParser::IdentifierNode::LOCAL_VARIABLE: {
			source = identifier->variable_source;
		} break;
		case GDScriptParser::IdentifierNode::LOCAL_ITERATOR: {
			source = identifier->bind_source;
		} break;
		default:
			break;