remove linejoin shader

The previous commit switched to using triangles for drawing round joins.

src/mbgl/map/tile_parser.cpp

@@ -172,8 +172,7 @@ std::unique_ptr<Bucket> TileParser::createFillBucket(const GeometryTileLayer& la
 std::unique_ptr<Bucket> TileParser::createLineBucket(const GeometryTileLayer& layer,
                                                      const StyleBucket& bucket_desc) {
     auto bucket = util::make_unique<LineBucket>(tile.lineVertexBuffer,
-                                                tile.triangleElementsBuffer,
-                                                tile.pointElementsBuffer);
+                                                tile.triangleElementsBuffer);
 
     const float z = tile.id.z;
     auto& layout = bucket->layout;