Bug 22098: (follow-up) fix grammar/formating Perldoc

Bug 22098: (follow-up) fix grammar/formating Perldoc

- nubers => numbers
- some vertical spacing
- !}fmt -w65
- "contains of letters" => "containing letters"

TEST PLAN
---------
perldoc cataloguing/value_builder/stocknumberAV.pl
apply patch
perldoc cataloguing/value_builder/stocknumberAV.pl
-- after the patch is more readable.

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>