### 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 (!p_preload->path) {
		return;
	}
	reduce_expression(p_preload->path);
	if (!p_preload->path->is_constant) {
		push_error("Preloaded path must be a constant string.", p_preload->path);
		return;
	}
	if (p_preload->path->reduced_value.get_type() != Variant::STRING) {
		push_error("Preloaded path must be a constant string.", p_preload->path);
	} else {
		p_preload->resolved_path = p_preload->path->reduced_value;
		
		if (p_preload->resolved_path.is_relative_path()) {
			p_preload->resolved_path = parser->script_path.get_base_dir().path_join(p_preload->resolved_path);
		}
		p_preload->resolved_path = p_preload->resolved_path.simplify_path();
		if (!ResourceLoader::exists(p_preload->resolved_path)) {
			Ref<FileAccess> file_check = FileAccess::create(FileAccess::ACCESS_RESOURCES);
			if (file_check->file_exists(p_preload->resolved_path)) {
				push_error(vformat(R"(Preload file "%s" has no resource loaders (unrecognized file extension).)", p_preload->resolved_path), p_preload->path);
			} else {
				push_error(vformat(R"(Preload file "%s" does not exist.)", p_preload->resolved_path), p_preload->path);
			}
		} else {
			
			
			
			if (ResourceLoader::get_resource_type(p_preload->resolved_path) == "GDScript") {
				Error err = OK;