### 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)

for (int i = 0; i < p_array->elements.size(); i++) {
		GDScriptParser::ExpressionNode *element = p_array->elements[i];
		reduce_expression(element);
	}
	
	GDScriptParser::DataType arr_type;
	arr_type.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	arr_type.kind = GDScriptParser::DataType::BUILTIN;
	arr_type.builtin_type = Variant::ARRAY;
	arr_type.is_constant = true;
	p_array->set_datatype(arr_type);
}
#ifdef DEBUG_ENABLED
static bool enum_has_value(const GDScriptParser::DataType p_type, int64_t p_value) {