### 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)

update_const_expression_builtin_type(p_return->return_value, expected_type, "return");
			}
			result = p_return->return_value->get_datatype();
		}
	} else {
		
		result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
		result.kind = GDScriptParser::DataType::BUILTIN;
		result.builtin_type = Variant::NIL;
		result.is_constant = true;
	}
	if (has_expected_type && !expected_type.is_variant()) {
		if (result.is_variant() || !result.is_hard_type()) {
			mark_node_unsafe(p_return);
			if (!is_type_compatible(expected_type, result, true, p_return)) {
				downgrade_node_type_source(p_return);
			}
		} else if (!is_type_compatible(expected_type, result, true, p_return)) {
			mark_node_unsafe(p_return);
			if (!is_type_compatible(result, expected_type)) {
				push_error(vformat(R"(Cannot return value of type "%s" because the function return type is "%s".)", result.to_string(), expected_type.to_string()), p_return);
			}
#ifdef DEBUG_ENABLED
		} else if (expected_type.builtin_type == Variant::INT && result.builtin_type == Variant::FLOAT) {
			parser->push_warning(p_return, GDScriptWarning::NARROWING_CONVERSION);
#endif
		}
	}
	p_return->set_datatype(result);
}