### 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)

ERR_FAIL_COND(!p_class->has_member(p_name));
	resolve_class_member(p_class, p_class->members_indices[p_name], p_source);
}
void GDScriptAnalyzer::resolve_class_member(GDScriptParser::ClassNode *p_class, int p_index, const GDScriptParser::Node *p_source) {
	ERR_FAIL_INDEX(p_index, p_class->members.size());
	GDScriptParser::ClassNode::Member &member = p_class->members.write[p_index];
	if (p_source == nullptr && parser->has_class(p_class)) {
		p_source = member.get_source_node();
	}
	if (member.get_datatype().is_resolving()) {
		push_error(vformat(R"(Could not resolve member "%s": Cyclic reference.)", member.get_name()), p_source);
		return;
	}
	if (member.get_datatype().is_set()) {
		return;
	}
	if (!parser->has_class(p_class)) {
		String script_path = p_class->get_datatype().script_path;
		Ref<GDScriptParserRef> parser_ref = get_parser_for(script_path);
		if (parser_ref.is_null()) {
			push_error(vformat(R"(Could not find script "%s" (While resolving "%s").)", script_path, member.get_name()), p_source);
			return;
		}