Due to a thinko in the patch for bug#77173, Help buffer highlights
_every_ instance of the word customize in the Help buffer.  To
reproduce,

  1. emacs -Q
  2. C-h v icomplete-vertical-selected-prefix-indicator RET
  3. Witness how the word "customized" in the docstring is partially
     buttonised.

The attached patch restricts the fontification to the customize blurb.