Bug 21698: Fix POD of cancel_unfilled_holds.pl

Bug 21698: Fix POD of cancel_unfilled_holds.pl

To test:
- Run "perldoc misc/cronjobs/holds/cancel_unfilled_holds.pl"
- Notice some problems:
-- No description in the NAME section
-- Descriptions of options in the SYNOPSIS section
-- A literal head1
-- Long options are listed with a single leading dash
-- Options --verbose and --confirm are not listed under OPTIONS)
- Take a look at the script itself to see that --verbose and
  --confirm should be listed.
- Also note the typo on line 97: 'v|verbosev' => \$verbose,
- Apply the patch
- Look at the script and perldoc again and check that all problems
  described above are now fixed.

Signed-off-by: Andrew Isherwood <andrew.isherwood@ptfs-europe.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit b7b6727f92615bcebf2f037202e6647a34c7705a)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 77969527962b4f8c098b59f50989bbea26831803)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>