Bug 11799: Housekeeping: Remove _biblionumber_sth from VirtualShelves.pm

This routine is no longer used.

Test plan:
Do a grep on the name.
(Bonus points:) Verify if you can perform some actions on lists.

No more occurences of _biblionumber_sth found
Signed-off-by: Marc Véron <veron@veron.ch>

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>

C4/VirtualShelves.pm

@@ -666,17 +666,6 @@ sub _shelf_count {
     return $total;
 }
 
-sub _biblionumber_sth { #only used in obsolete sub below
-    my ($shelf) = @_;
-    my $query = 'select biblionumber from virtualshelfcontents where shelfnumber = ?';
-    my $dbh = C4::Context->dbh;
-    my $sth = $dbh->prepare($query)
-        or die $dbh->errstr;
-    $sth->execute( $shelf )
-        or die $sth->errstr;
-    $sth;
-}
-
 sub _CheckShelfName {
     my ($name, $cat, $owner, $number)= @_;