### 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)

Dictionary dictionary;
	for (int i = 0; i < p_dictionary->elements.size(); i++) {
		const GDScriptParser::DictionaryNode::Pair &element = p_dictionary->elements[i];
		bool is_element_key_reduced = false;
		Variant element_key = make_expression_reduced_value(element.key, is_element_key_reduced);
		if (!is_element_key_reduced) {
			return Variant();
		}
		bool is_element_value_reduced = false;
		Variant element_value = make_expression_reduced_value(element.value, is_element_value_reduced);
		if (!is_element_value_reduced) {
			return Variant();
		}
		dictionary[element_key] = element_value;
	}
	dictionary.make_read_only();
	is_reduced = true;
	return dictionary;
}
Variant GDScriptAnalyzer::make_subscript_reduced_value(GDScriptParser::SubscriptNode *p_subscript, bool &is_reduced) {