version 1.52.4 release

Compatible with NetworkManager 1.52.2, 1.54.3 or 1.56.0 and later.

Summary of changes since NetworkManager-l2tp 1.52.4:

• Parser-hardening of control characters in username, VPN data-items and secrets along with PLUTODEBUG and CHARONDEBUG env vars.
• Disable MPPE option in editor whenever IPsec is enabled.
• Remove deprecated KDE Plasma-nm L2TP certificate support.
• Updated translations.