tmc e2e: put the sink worksace on the root shard

... until the TMC e2e tests are made shard-aware.

Signed-off-by: David Festal <dfestal@redhat.com>

test/e2e/framework/kcp.go

@@ -862,7 +862,7 @@ func newPersistentKCPServer(name, kubeconfigPath string, shardKubeconfigPaths ma
 func NewFakeWorkloadServer(t *testing.T, server RunningServer, org logicalcluster.Path, syncTargetName string) RunningServer {
 	t.Helper()
 
-	path, ws := NewWorkspaceFixture(t, server, org, WithName(syncTargetName+"-sink"))
+	path, ws := NewWorkspaceFixture(t, server, org, WithName(syncTargetName+"-sink"), TODO_WithoutMultiShardSupport())
 	logicalClusterName := logicalcluster.Name(ws.Spec.Cluster)
 	rawConfig, err := server.RawConfig()
 	require.NoError(t, err, "failed to read config for server")