Delete unused TriangleLabelView license (#6965)

app/src/main/assets/LICENSE_TRIANGLE_LABEL_VIEW.txt

@@ -1,13 +0,0 @@
-Copyright (C) 2016 Shota Saito
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-     http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.