SPEC: don't fail uninstallation if 'alternatives' fails

This is seen on rpm-ostree based system during uninstall:
```
Running scriptlet: sssd-client-2.9.5-4.el9.x86_64 9/9
admindir /var/lib/alternatives invalid
error: %preun(sssd-client-2.9.5-4.el9.x86_64) scriptlet failed, exit status 2
```

This should be fixed by fedora-sysv/chkconfig#135
but let's avoid hard failing here anyway.

contrib/sssd.spec.in

@@ -1167,7 +1167,7 @@ getent passwd sssd >/dev/null || useradd -r -g sssd -d / -s /sbin/nologin -c "Us
 
 %preun client
 if [ $1 -eq 0 ] ; then
-        /usr/sbin/alternatives --remove cifs-idmap-plugin %{_libdir}/cifs-utils/cifs_idmap_sss.so
+        /usr/sbin/alternatives --remove cifs-idmap-plugin %{_libdir}/cifs-utils/cifs_idmap_sss.so || true
 fi
 
 %posttrans common