### 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)

if (subscript->base->type == GDScriptParser::Node::IDENTIFIER) {
			base_id = static_cast<GDScriptParser::IdentifierNode *>(subscript->base);
		}
		if (base_id && GDScriptParser::get_builtin_type(base_id->name) < Variant::VARIANT_MAX) {
			base_type = make_builtin_meta_type(GDScriptParser::get_builtin_type(base_id->name));
		} else {
			reduce_expression(subscript->base);
			base_type = subscript->base->get_datatype();
			is_self = subscript->base->type == GDScriptParser::Node::SELF;
		}
	} else {
		
		
		p_call->set_datatype(call_type);
		mark_node_unsafe(p_call);
		return;
	}
	int default_arg_count = 0;
	BitField<MethodFlags> method_flags;
	GDScriptParser::DataType return_type;
	List<GDScriptParser::DataType> par_types;
	bool is_constructor = (base_type.is_meta_type || (p_call->callee && p_call->callee->type == GDScriptParser::Node::IDENTIFIER)) && p_call->function_name == SNAME("new");
	if (get_function_signature(p_call, is_constructor, base_type, p_call->function_name, return_type, par_types, default_arg_count, method_flags)) {
		
		
		if (method_flags.has_flag(METHOD_FLAG_VIRTUAL)) {
			if (p_call->is_super) {
				push_error(vformat(R"*(Cannot call the parent class' virtual function "%s()" because it hasn't been defined.)*", p_call->function_name), p_call);
			} else {
				push_error(vformat(R"*(Cannot call virtual function "%s()" because it hasn't been defined.)*", p_call->function_name), p_call);