terraform: fixes the plugins

The plugins are now part of the binary and cause conflict when available
in the $PATH as well.

pkgs/applications/networking/cluster/terraform/default.nix

···
   };
 
   postInstall = ''
-    # prefix all the plugins with "terraform-"
+    # remove all plugins, they are part of the main binary now
     for i in $bin/bin/*; do
       if [[ $(basename $i) != terraform ]]; then
-        mv -v $i $bin/bin/terraform-$(basename $i);
+        rm "$i"
       fi
     done
   '';