### 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)

reduce_expression(p_ternary_op->condition);
	reduce_expression(p_ternary_op->true_expr, p_is_root);
	reduce_expression(p_ternary_op->false_expr, p_is_root);
	GDScriptParser::DataType result;
	if (p_ternary_op->condition && p_ternary_op->condition->is_constant && p_ternary_op->true_expr->is_constant && p_ternary_op->false_expr && p_ternary_op->false_expr->is_constant) {
		p_ternary_op->is_constant = true;
		if (p_ternary_op->condition->reduced_value.booleanize()) {
			p_ternary_op->reduced_value = p_ternary_op->true_expr->reduced_value;
		} else {
			p_ternary_op->reduced_value = p_ternary_op->false_expr->reduced_value;
		}
	}