Remove dotgraph feature (#2848)

Apparently the implementation is broken and is generating warnings in
the build. Not sure this was used any way by anyone.

Closes: #2836

Author: bkchr

Cargo.lock

@@ -40,7 +40,6 @@ tikv-jemalloc-ctl = "0.5.0"
 
 [features]
 default = ["futures_channel"]
-dotgraph = ["orchestra/dotgraph"]
 expand = ["orchestra/expand"]
 futures_channel = ["metered/futures_channel", "orchestra/futures_channel"]
 jemalloc-allocator = ["dep:tikv-jemalloc-ctl"]