bug#30659: Only local map define-key examples

["積丹尼 Dan Jacobson" <jidanni@jidanni.org>]

(info "(emacs) Init Examples")
only has
          (global-unset-key "\C-x\C-v")
example.

(info "(emacs) Rebinding") mentions
‘M-x global-unset-key <RET> KEY’
     Make KEY undefined in the global map.
‘M-x local-unset-key <RET> KEY’
     Make KEY undefined locally (in the major mode now in effect).


However they all lack proper local map .emacs undefine key examples.

An undefine local key example needs to be wrapped in the proper hook,
else, unlike a global undefine key example, it will not work.

And, without such proper tested working example in the manual, I cannot
proceed in unbinding local keys. Thank you.