downgrade barrier to 2.3.4

2.4 has too many issues: https://github.com/debauchee/barrier/issues?q=is%3Aissue+is%3Aopen+2.4+

especially security issue that SSL doesn' t work: https://github.com/debauchee/barrier/issues/1438

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: barrier 2.4.0+dfsg-2
ProcVersionSignature: Ubuntu 5.15.0-40.43-generic 5.15.35
Uname: Linux 5.15.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Thu Jul 14 15:19:05 2022
InstallationDate: Installed on 2019-05-06 (1165 days ago)
InstallationMedia: Ubuntu 16.04.6 LTS "Xenial Xerus" - Release amd64 (20190227)
RebootRequiredPkgs: Error: path contained symlinks.
SourcePackage: barrier
UpgradeStatus: Upgraded to jammy on 2022-04-19 (85 days ago)