bug#28550: 25.2; Hydra: First example hydra in the docs doesn't work

[Oleh Krehel]

Please try to reproduce with my steps (especially emacs -Q and
remove/reinstall). There's likely no reason for this code to stop
working other than byte-compilation or config bug: it's worked fine
for 2 months without anyone else complaining.

If I can't reproduce it on my side, I can't do much.