### 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)

GDScriptParser::DataType class_type;
	class_type.is_constant = true;
	class_type.is_meta_type = true;
	class_type.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
	class_type.kind = GDScriptParser::DataType::CLASS;
	class_type.class_type = p_class;
	class_type.script_path = parser->script_path;
	class_type.builtin_type = Variant::OBJECT;
	p_class->set_datatype(class_type);
	GDScriptParser::DataType result;
	if (!p_class->extends_used) {
		result.type_source = GDScriptParser::DataType::ANNOTATED_INFERRED;
		result.kind = GDScriptParser::DataType::NATIVE;
		result.native_type = SNAME("RefCounted");
	} else {
		result.type_source = GDScriptParser::DataType::ANNOTATED_EXPLICIT;
		GDScriptParser::DataType base;
		int extends_index = 0;
		if (!p_class->extends_path.is_empty()) {
			if (p_class->extends_path.is_relative_path()) {
				p_class->extends_path = class_type.script_path.get_base_dir().path_join(p_class->extends_path).simplify_path();
			}
			Ref<GDScriptParserRef> ext_parser = get_parser_for(p_class->extends_path);
			if (ext_parser.is_null()) {
				push_error(vformat(R"(Could not resolve super class path "%s".)", p_class->extends_path), p_class);
				return ERR_PARSE_ERROR;
			}
			Error err = ext_parser->raise_status(GDScriptParserRef::INHERITANCE_SOLVED);
			if (err != OK) {
				push_error(vformat(R"(Could not resolve super class inheritance from "%s".)", p_class->extends_path), p_class);