Bug 37319: Move mappings for 752ad (MARC21) and 210a/214a (UNIMARC) to pl index

Bug 37319: Move mappings for 752ad (MARC21) and 210a/214a (UNIMARC) to pl index

In Bug 36578, some fields were added to the pl index, but somehow it
ended up in the other-control-number index. This aims to put fields
752ad (MARC21) and 210a/214a (UNIMARC) in the pl index.

Test plan:
----------
0. Have an installation with Elasticsearch and MARC 21 configuration.
1. Under  Administration > Search engine configuration (Elasticsearch)
   under the tab Bibliographic records check that you have 752ad in
   other-control-number search field.
2. Apply the patch, reindex with:
   sudo koha-elasticsearch --rebuild -r -b kohadev
3. Under  Administration > Search engine configuration (Elasticsearch)
   under the tab Bibliographic records check that you have 752ad in pl
   search field now.

Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>