### 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)

}
	}
}
void GDScriptAnalyzer::reduce_unary_op(GDScriptParser::UnaryOpNode *p_unary_op) {
	reduce_expression(p_unary_op->operand);
	GDScriptParser::DataType result;
	if (p_unary_op->operand == nullptr) {
		result.kind = GDScriptParser::DataType::VARIANT;
		p_unary_op->set_datatype(result);
		return;
	}
	GDScriptParser::DataType operand_type = p_unary_op->operand->get_datatype();
	if (p_unary_op->operand->is_constant) {
		p_unary_op->is_constant = true;
		p_unary_op->reduced_value = Variant::evaluate(p_unary_op->variant_op, p_unary_op->operand->reduced_value, Variant());
		result = type_from_variant(p_unary_op->reduced_value, p_unary_op);
	}
	if (operand_type.is_variant()) {
		result.kind = GDScriptParser::DataType::VARIANT;
		mark_node_unsafe(p_unary_op);
	} else {
		bool valid = false;
		result = get_operation_type(p_unary_op->variant_op, operand_type, valid, p_unary_op);
		if (!valid) {
			push_error(vformat(R"(Invalid operand of type "%s" for unary operator "%s".)", operand_type.to_string(), Variant::get_operator_name(p_unary_op->variant_op)), p_unary_op);
		}
	}
	p_unary_op->set_datatype(result);
}
Variant GDScriptAnalyzer::make_expression_reduced_value(GDScriptParser::ExpressionNode *p_expression, bool &is_reduced) {