python-gnupg: bump to 0.5.6

python-gnupg: bump to 0.5.6

Changelog since 0.5.1:
- Add configurable I/O buffer size via buffer_size attribute (0.5.2)
- Add Web Key Directory (WKD) support for automatic key location (0.5.3)
- Fix sensitive data exposure by removing decryption result logging (0.5.3)
- Fix exception handling in on_data callable during GPG operations (0.5.4)
- Fix GPG version detection robustness (0.5.5)
- Add uid_map attribute to capture UID information (0.5.5)
- Add capability, fingerprint and keygrip to subkey_info (0.5.6)
- Fix username handling when verification keys are expired/revoked (0.5.6)

Full changelog:
https://github.com/vsajip/python-gnupg/releases

Signed-off-by: Alexandru Ardelean <redacted>