Bug 30974: Set size for indexing jobs to 1

job's size is the number of records to index, but when finished the progress is always set to 1.

Wich leads to: finished 1/42

Test plan:
Don't apply this patch
Use the batch item modification tool to update more than 1 item
Notice that the new indexing job has a size of the number of items you
modified
When finished, the job detail shows "Finished. 1/X"
Apply this patch, repeat
Notice that now the progress shows 0/1 before the job is done, then 1/1
when finished

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 85dc90c151)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>

Koha/BackgroundJob/UpdateElasticIndex.pm

@@ -107,7 +107,7 @@ sub enqueue {
     my @record_ids = @{ $args->{record_ids} };
 
     $self->SUPER::enqueue({
-        job_size => scalar @record_ids,
+        job_size => 1,
         job_args => {record_server => $record_server, record_ids => \@record_ids},
     });
 }