Fix length of field 100$a in some UNIMARC records

See https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=38908

The 100$a field for some UNIMARC records have 35 bytes and not 36. It breaks Elasticsearch indexing. It concerns biblionumbers 1651, 336, 3116, 4001, 3950, 3685, 4141, 3012, 3700, 212