### 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)

callee_id = static_cast<GDScriptParser::IdentifierNode *>(p_call->callee);
			} else {
				
				callee_id = static_cast<GDScriptParser::SubscriptNode *>(p_call->callee)->attribute;
			}
			if (callee_id) {
				reduce_identifier_from_base(callee_id, &base_type);
				GDScriptParser::DataType callee_datatype = callee_id->get_datatype();
				if (callee_datatype.is_set() && !callee_datatype.is_variant()) {
					found = true;
					if (callee_datatype.builtin_type == Variant::CALLABLE) {
						push_error(vformat(R"*(Name "%s" is a Callable. You can call it with "%s.call()" instead.)*", p_call->function_name, p_call->function_name), p_call->callee);
					} else {
						push_error(vformat(R"*(Name "%s" called as a function but is a "%s".)*", p_call->function_name, callee_datatype.to_string()), p_call->callee);
					}
#ifdef DEBUG_ENABLED
				} else if (!is_self && !(base_type.is_hard_type() && base_type.kind == GDScriptParser::DataType::BUILTIN)) {
					parser->push_warning(p_call, GDScriptWarning::UNSAFE_METHOD_ACCESS, p_call->function_name, base_type.to_string());
					mark_node_unsafe(p_call);
#endif
				}
			}
		}
		if (!found && (is_self || (base_type.is_hard_type() && base_type.kind == GDScriptParser::DataType::BUILTIN))) {
			String base_name = is_self && !p_call->is_super ? "self" : base_type.to_string();
#ifdef SUGGEST_GODOT4_RENAMES
			String rename_hint = String();
			if (GLOBAL_GET(GDScriptWarning::get_settings_path_from_code(GDScriptWarning::Code::RENAMED_IN_GODOT_4_HINT)).booleanize()) {
				const char *renamed_function_name = check_for_renamed_identifier(p_call->function_name, p_call->type);
				if (renamed_function_name) {