Fix grep ambiguities

See also:

    https://github.com/koalaman/shellcheck/issues/1342

dotfiles/bash/setup

 }
 
 mark="# added by https://github.com/AloisMahdal/mydots"
-if grep -qF "$mark" "$HOME/.bashrc";
+if grep -qFe "$mark" "$HOME/.bashrc";
 then
     echo "already set up, giving up";
     exit 1;