### 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 index = extends_index; index < p_class->extends.size(); index++) {
			GDScriptParser::IdentifierNode *id = p_class->extends[index];
			if (base.kind != GDScriptParser::DataType::CLASS) {
				push_error(vformat(R"(Cannot get nested types for extension from non-GDScript type "%s".)", base.to_string()), id);
				return ERR_PARSE_ERROR;
			}
			reduce_identifier_from_base(id, &base);
			GDScriptParser::DataType id_type = id->get_datatype();
			if (!id_type.is_set()) {
				push_error(vformat(R"(Could not find nested type "%s".)", id->name), id);
				return ERR_PARSE_ERROR;
			} else if (id_type.kind != GDScriptParser::DataType::SCRIPT && id_type.kind != GDScriptParser::DataType::CLASS) {
				push_error(vformat(R"(Identifier "%s" is not a preloaded script or class.)", id->name), id);
				return ERR_PARSE_ERROR;
			}
			base = id_type;
		}
		result = base;
	}
	if (!result.is_set() || result.has_no_type()) {
		
		push_error(vformat(R"(Could not resolve inheritance for class "%s".)", p_class->identifier == nullptr ? "<main>" : p_class->identifier->name), p_class);
		return ERR_PARSE_ERROR;
	}
	
	const GDScriptParser::ClassNode *base_class = result.class_type;
	while (base_class) {