Fixed upgrade warnings in SpeedTree8 subgraphs. (#6160)

Author: phi-lira

com.unity.shadergraph/CHANGELOG.md

@@ -29,7 +29,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
  - Fixed a bug where node preview doesn't update when a texture is changed in the explorer [1363784](https://issuetracker.unity3d.com/product/unity/issues/guid/1363784/)
  - Fixed missing shader keyword stage during keyword copying.
  - Fixed a ShaderGraph warning when connecting a node using Object Space BiTangent to the vertex stage [1361512] (https://issuetracker.unity3d.com/issues/shader-graph-cross-implicit-truncation-of-vector-type-errors-are-thrown-when-connecting-transform-node-to-vertex-block)
-
+ - Fixed upgrade warnings on SpeedTree8 subgraphs.
 
 ## [13.1.0] - 2021-09-24