Liquid GDK 0.77.4

Release 0.77.4 - 26-05-22

Added

• Singlesig: Add new GDK errors when rate limited by Electrum.

Changed

• Dependencies: Update Rust dependencies rand, openssl and rustls-webpki.

Fixed

• Singlesig: Fix get_unspent_outputs returning just-spent utxos before getting new utxos from sync.
• Build: Small fixes for OpenSSL build and JAVA_HOME variable usage.