[#47] client: Do not check context in NetmapSnapshot()

It is passed explicitly, non-nil by convention.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

client/netmap_test.go

@@ -69,11 +69,6 @@ func TestClient_NetMapSnapshot(t *testing.T) {
 	c := newClient(&srv)
 	ctx := context.Background()
 
-	// missing context
-	//nolint:staticcheck
-	_, err = c.NetMapSnapshot(nil, prm)
-	require.ErrorIs(t, err, errorMissingContext, "")
-
 	// request signature
 	srv.errTransport = errors.New("any error")