message: Fix broken graphviz download link and change to https
  The graphviz download link has been changed to
  This fix fixes the broken link in jit.md.
diff: @@ -157,7 +157,7 @@ to fuse Ops is visible by starting at `hlo_graph_0.dot` and viewing each diagram
  in succession.
  To Render the .dot file into a png, install
  -[GraphViz](http://www.graphviz.org/Download..php) and run:
  +[GraphViz](https://www.graphviz.org/download/) and run:
  ```shell
  dot -Tpng hlo_graph_80.dot -o hlo_graph_80.png
  