Fixed Composer license info and bumped license & copyright year

[alongosz]

$ composer validate
./composer.json is valid, but with a few warnings
See https://getcomposer.org/doc/04-schema.md for details on the schema
# General warnings
- License "GPL-2.0" is a deprecated SPDX license identifier, use "GPL-2.0-only" or "GPL-2.0-or-later" instead

We have GPL + BUL type of licensing, therefore updated as it should be.

while at it, I updated year to 2024.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

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