Bug 32779: ERM - Fix import from list

There is a typo, '$' is missing, which caused the following error:
Use of inherited AUTOLOAD for non-method Koha::BackgroundJob::CreateEHoldingsFromBiblios::fix_coverage() is no longer allowed at /kohadevbox/koha/Koha/BackgroundJob/CreateEHoldingsFromBiblios.pm line 126

Test plan:
Create a list, add an item
Turn on ERM
Create a package
Go to /cgi-bin/koha/erm/eholdings/local/titles
Click "Import from list"
Select the package, then your list, and import
It should succeed

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

Koha/BackgroundJob/CreateEHoldingsFromBiblios.pm

@@ -124,7 +124,7 @@ sub process {
             my ( $date_first_issue_online, $date_last_issue_online ) =
               $fix_coverage->( $record->subfield( '866', 'a' ) );
             my ( $num_first_vol_online, $num_last_vol_online ) =
-              fix_coverage->( $record->subfield( '863', 'a' ) );
+              $fix_coverage->( $record->subfield( '863', 'a' ) );
             my ( $num_first_issue_online, $num_last_issue_online ) =
               ( '', '' );    # FIXME ?
             my $title_url = $record->subfield( '856', 'u' );