Bug 36247: MARC21 Addition to relator terms in technical notice 2024-02-27

Bug 36247: MARC21 Addition to relator terms in technical notice 2024-02-27

This patch adds the relator code gdv (Game developer) in the list of
MARC21 relator terms in Koha.

To test:
1. Apply patch and reset_all
2. Go to Administration > Authorized values > RELTERMS
3. Search for gdv
   --> The new relator code should be there with its corresponding term
       "Game developer"

Note: this is added in the installer files. It will not affect existing
installations. For existing installations, add the new relator code in
Administration > Authorized values > RELTERMS.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>