bug#30001: 27.0.50; Outdated info on save-excursion in (info "(cl) Modify Macros")

[Xu Chunyang]

'C-h S cl-letf' or (info "(cl) Modify Macros") has the following:

  Note that `cl-letf' on `(point)' is not quite like a
  `save-excursion', as the latter effectively saves a marker which
  tracks insertions and deletions in the buffer.

but 'save-excursion' is no longer saving marker since Emacs 25.1
according to 'C-h f save-excursion'.