security/py-securesystemslib: Update version 0.28.0=>0.29.0

Changelog:
https://github.com/secure-systems-lab/securesystemslib/releases/tag/v0.29.0

security/py-securesystemslib/Makefile

 PORTNAME=	securesystemslib
-PORTVERSION=	0.28.0
+PORTVERSION=	0.29.0
 CATEGORIES=	security python
 MASTER_SITES=	PYPI
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}

security/py-securesystemslib/distinfo

-TIMESTAMP = 1681924414
-SHA256 (securesystemslib-0.28.0.tar.gz) = a27e519247576f2a77b97fb03267d8eeb88eba715d12da64109e845616f919c6
-SIZE (securesystemslib-0.28.0.tar.gz) = 994910
+TIMESTAMP = 1694064204
+SHA256 (securesystemslib-0.29.0.tar.gz) = dcfcb70562ad76069f71da9916a3cb7bc85fbf6cd51216c741a00096cf58dc6c
+SIZE (securesystemslib-0.29.0.tar.gz) = 1007216