### 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)

return err;
			}
			base = ext_parser->get_parser()->head->get_datatype();
		} else {
			if (p_class->extends.is_empty()) {
				push_error("Could not resolve an empty super class path.", p_class);
				return ERR_PARSE_ERROR;
			}
			GDScriptParser::IdentifierNode *id = p_class->extends[extends_index++];
			const StringName &name = id->name;
			base.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
			if (ScriptServer::is_global_class(name)) {
				String base_path = ScriptServer::get_global_class_path(name);
				if (base_path == parser->script_path) {
					base = parser->head->get_datatype();
				} else {
					Ref<GDScriptParserRef> base_parser = get_parser_for(base_path);
					if (base_parser.is_null()) {
						push_error(vformat(R"(Could not resolve super class "%s".)", name), id);
						return ERR_PARSE_ERROR;
					}
					Error err = base_parser->raise_status(GDScriptParserRef::INHERITANCE_SOLVED);
					if (err != OK) {
						push_error(vformat(R"(Could not resolve super class inheritance from "%s".)", name), id);
						return err;
					}
					base = base_parser->get_parser()->head->get_datatype();
				}
			} else if (ProjectSettings::get_singleton()->has_autoload(name) && ProjectSettings::get_singleton()->get_autoload(name).is_singleton) {
				const ProjectSettings::AutoloadInfo &info = ProjectSettings::get_singleton()->get_autoload(name);