packaging: fix snap build

Support for package repositories is no longer experimental, and the
--enable-experimental-package-repositories flag has been removed as of
Snapcraft 4.8.

Change-Id: Ie095aaef7806a13ba765941bed480a25f8cae552

scripts/build-package-snap.sh

@@ -29,7 +29,7 @@ cd /opt/ring-project/packaging/rules/snap/${SNAP_PKG_NAME}/
 # set the version and tarball filename
 sed -i "s/RELEASE_VERSION/${RELEASE_VERSION}/g" snapcraft.yaml
 
-snapcraft --enable-experimental-package-repositories # requires snapcraft >= 4.4
+snapcraft # requires snapcraft >= 4.8
 
 # move the built snap to output
 mv *.snap /opt/output/