Update README.md remove github button

Author: HaleySchuhl

README.md

@@ -6,10 +6,7 @@
 
 [![Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/danforthcenter/plantcv-tutorial-threshold/blob/main/index-colab.ipynb)
 
-[![Static Badge](https://img.shields.io/badge/Open%20in%20GitHub-black?logo=github)](https://github.com/danforthcenter/plantcv-tutorial-threshold)
-
 ## Tutorial tags/keywords
 
 thresholding, segmentation, masking
 
-## Citations