update: libtasn1

**Name**: libtasn1
**CVEs**: [CVE-2025-13151](https://www.cve.org/CVERecord?id=CVE-2025-13151)
**CVSSs**: 7.5
**Action Needed**: update to >= 4.21.0

**Summary**: Stack-based buffer overflow in libtasn1 version: v4.20.0. The function fails to validate the size of input data resulting in a buffer overflow in asn1_expend_octet_string.

**refmap.gentoo**: https://bugs.gentoo.org/968531
