mail/sympa: update 6.5.2 -> 6.2.54 with security fix

PR: 245672
Submitted by: geoffroy desvernay <dgeo@centrale-marseille.fr> (maintainer)
MFH: 2020Q2
Relnotes: https://github.com/sympa-community/sympa/blob/6.2.54/NEWS.md
Security: CVE-2020-9369