Use MSC2716 room version that exists

During the development of matrix-org/synapse#11243
we added a `org.matrix.msc2716v4` room version but it's no longer necessary
and was removed in matrix-org/synapse@e2928b5

tests/msc2716_test.go

@@ -50,13 +50,13 @@ var (
 var createPublicRoomOpts = map[string]interface{}{
 	"preset":       "public_chat",
 	"name":         "the hangout spot",
-	"room_version": "org.matrix.msc2716v4",
+	"room_version": "org.matrix.msc2716v3",
 }
 
 var createPrivateRoomOpts = map[string]interface{}{
 	"preset":       "private_chat",
 	"name":         "the hangout spot",
-	"room_version": "org.matrix.msc2716v4",
+	"room_version": "org.matrix.msc2716v3",
 }
 
 func TestImportHistoricalMessages(t *testing.T) {