files/linux-pam-config: make pwquality optional

we don't build it in freedesktop-sdk
8 jobs for abderrahim/pwquality in 184 minutes and 18 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Flatpak
passed #215681194
aarch64
app_aarch64

03:01:07

passed #215681196
armhf
app_arm

01:10:33

passed #215681191
cache_i686 x86_64
app_i686

01:59:18

passed #215681189
cache_x86_64 x86_64
app_x86_64

01:56:16

 
  Vm
manual #215681199
aarch64 allowed to fail manual
minimal_systemd_vm_aarch64
passed #215681200
armhf
minimal_systemd_vm_arm

00:03:10

passed #215681198
cache_i686 x86_64
minimal_systemd_vm_i686

00:01:50

passed #215681197
cache_x86_64 x86_64
minimal_systemd_vm_x86_64

00:01:57