Doesn't respect flatpak's enumerate/don't enumerate settings

### What Happened?

Flatpak has the ability to mark certain repositories as "no-enumerate." Here is the setup on my machine:
```
$ flatpak remotes
Name Options
appcenter system
flathub system
freedesktop system,no-enumerate,filtered
appcenter user
flathub user,no-enumerate
```

### Steps to Reproduce

To reproduce, install an app from FlatHub that requires dependencies. Flatpak will automatically add the flathub repository and therefore all of the apps from flathub will appear in AppCenter. This is something that most people sideloading flatpak apps probably want --- however, for users like me that are completely comfortable with manually sideloading flatpak apps, the settings of flatpak should be respected, so that the AppCenter only contains the elegant and curated apps from the elementary team.

### Expected Behavior

From `man 1 flatpak-remote-modify`:

`--no-enumerate`
Mark the remote as not enumerated. This means the remote will not be used to list applications, **for instance in graphical installation tools**. It will also not be used for runtime dependency resolution (as with --no-use-for-deps).

With this setting enabled, as described, AppCenter should not list from this repository in the search listing or in the different category lists

### OS Version

7.x (Horus)

### Software Version

Latest release (I have run all updates)

### Log Output

_No response_

### Hardware Info

_No response_