Drop Ubuntu 18.04, allow systemd 6.x #482

Job	Run time
Setup Test Matrix	23s
Puppet 8 (Ruby 3.2)	2m 58s
Puppet 7 (Ruby 2.7)	3m 27s
Puppet 8 - OracleLinux 8	20m 27s
Puppet 7 - OracleLinux 8	11m 38s
Puppet 8 - OracleLinux 9	10m 56s
Puppet 7 - OracleLinux 9	11m 40s
Puppet 8 - CentOS 7	15m 49s
Puppet 7 - CentOS 7	11m 40s
Puppet 8 - CentOS 8	20m 57s
Puppet 7 - CentOS 8	11m 46s
Puppet 8 - CentOS 9	11m 14s
Puppet 7 - CentOS 9	11m 43s
Puppet 8 - AlmaLinux 8	15m 14s
Puppet 7 - AlmaLinux 8	12m 27s
Puppet 8 - AlmaLinux 9	14m 11s
Puppet 7 - AlmaLinux 9	17m 27s
Puppet 8 - Rocky 8	14m 47s
Puppet 7 - Rocky 8	11m 34s
Puppet 8 - Rocky 9	14m 12s
Puppet 7 - Rocky 9	11m 59s
Puppet 8 - Debian 10	17m 6s
Puppet 7 - Debian 10	13m 49s
Puppet 8 - Debian 11	16m 46s
Puppet 7 - Debian 11	13m 7s
Puppet 8 - Ubuntu 20.04	20m 55s
Puppet 7 - Ubuntu 20.04	16m 44s
Puppet 8 - Ubuntu 22.04	22m 35s
Puppet 7 - Ubuntu 22.04	15m 43s
Distro Puppet - Archlinux rolling	1s
Test suite	0s
	6h 33m 15s

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