store: Fix semantic merge conflict

Not totally sure how this got through CI, but the most recent
two PRs semantically conflicted. Update the new code
to use the new glib prelude import.

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

ostree-ext/src/container/store.rs

@@ -20,10 +20,10 @@ use containers_image_proxy::{ImageProxy, OpenedImage};
 use flate2::Compression;
 use fn_error_context::context;
 use futures_util::TryFutureExt;
+use glib::prelude::*;
 use oci_spec::image::{
     self as oci_image, Arch, Descriptor, Digest, History, ImageConfiguration, ImageManifest,
 };
-use ostree::glib::FromVariant;
 use ostree::prelude::{Cast, FileEnumeratorExt, FileExt, ToVariant};
 use ostree::{gio, glib};
 use std::collections::{BTreeMap, BTreeSet, HashMap};