### 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)

if (valid) {
				p_subscript->is_constant = true;
				p_subscript->reduced_value = value;
				result_type = type_from_variant(value, p_subscript);
			}
		} else if (base_type.is_variant() || !base_type.is_hard_type()) {
			valid = !base_type.is_pseudo_type || p_can_be_pseudo_type;
			result_type.kind = GDScriptParser::DataType::VARIANT;
			if (base_type.is_variant() && base_type.is_hard_type() && base_type.is_meta_type && base_type.is_pseudo_type) {
				
				String enum_name;
				if (p_subscript->base->type == GDScriptParser::Node::IDENTIFIER) {
					enum_name = String(static_cast<GDScriptParser::IdentifierNode *>(p_subscript->base)->name) + ENUM_SEPARATOR + String(p_subscript->attribute->name);
				}
				if (CoreConstants::is_global_enum(enum_name)) {
					result_type = make_global_enum_type(enum_name, StringName());
				} else {
					valid = false;
					mark_node_unsafe(p_subscript);
				}
			} else {
				mark_node_unsafe(p_subscript);
			}
		} else {
			reduce_identifier_from_base(p_subscript->attribute, &base_type);
			GDScriptParser::DataType attr_type = p_subscript->attribute->get_datatype();
			if (attr_type.is_set()) {
				valid = !attr_type.is_pseudo_type || p_can_be_pseudo_type;
				result_type = attr_type;
				p_subscript->is_constant = p_subscript->attribute->is_constant;