### 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::DataType result;
	result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	result.kind = GDScriptParser::DataType::BUILTIN;
	result.builtin_type = Variant::BOOL;
	p_type_test->set_datatype(result);
	if (!p_type_test->operand || !p_type_test->test_type) {
		return;
	}
	reduce_expression(p_type_test->operand);
	GDScriptParser::DataType operand_type = p_type_test->operand->get_datatype();
	GDScriptParser::DataType test_type = type_from_metatype(resolve_datatype(p_type_test->test_type));
	p_type_test->test_datatype = test_type;
	if (!operand_type.is_set() || !test_type.is_set()) {
		return;
	}
	if (p_type_test->operand->is_constant) {
		p_type_test->is_constant = true;
		p_type_test->reduced_value = false;
		if (!is_type_compatible(test_type, operand_type)) {
			push_error(vformat(R"(Expression is of type "%s" so it can't be of type "%s".)", operand_type.to_string(), test_type.to_string()), p_type_test->operand);
		} else if (is_type_compatible(test_type, type_from_variant(p_type_test->operand->reduced_value, p_type_test->operand))) {
			p_type_test->reduced_value = test_type.builtin_type != Variant::OBJECT || !p_type_test->operand->reduced_value.is_null();
		}
		return;
	}
	if (!is_type_compatible(test_type, operand_type) && !is_type_compatible(operand_type, test_type)) {
		if (operand_type.is_hard_type()) {
			push_error(vformat(R"(Expression is of type "%s" so it can't be of type "%s".)", operand_type.to_string(), test_type.to_string()), p_type_test->operand);
		} else {
			downgrade_node_type_source(p_type_test->operand);