Bug 34077: Allow to use --category-code as the only filter option

Bug 34077: Allow to use --category-code as the only filter option

--category-code was not checked in the "at least one filter option"
check but it is clearly a filter option.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit d5cb77532ebbe01632f7f27046a2e86a03eac36b)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 5b5aa52547443361238f42041f7c17874a8a28bf)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>