Documentation Tweak: Octave Checks

[6d8fd379d7b549a5]

Hi,
I got confused by the Octave Checks documentation:
https://lilypond.org/doc/v2.22/Documentation/notation-big-page#octave-checks
https://gitlab.com/lilypond/lilypond/-/blob/d408cdc68629ef6df72de0d0ace9c460016565f8/Documentation/en/notation/pitches.itely#L706

I thought the ='4 was some special notation to specify the 4th octave 
(rather than the octave and then also the duration).

I guess, I could've realized that the duration needs to be specified 
somewhere,
but to save other users from also being potentially confused by this, I 
would suggest changing it from:
----
c''2 d='4 d
----

to just:
----
c''2 d='
----

That way it would also be more easily comparable to the \octaveCheck 
example right below it.


Cheers! :)