Bump zram-fraction to 2.0 for reproducible.archlinux.org

This box is very sussy and really likes to fill up its zram swap:

  [root@reproducible ~]# zramctl
  NAME       ALGORITHM DISKSIZE  DATA  COMPR TOTAL STREAMS MOUNTPOINT
  /dev/zram0 lzo-rle       1.9G  1.5G 183.4M  196M       1 [SWAP]

  [root@reproducible ~]# free -m
                 total        used        free      shared  buff/cache   available
  Mem:            1928         529          73           5        1325        1236
  Swap:           1927        1543         384

Fixes: 4a5748ea ("Bump zram-fraction to 1.0 for reproducible.archlinux.org")

host_vars/reproducible.archlinux.org/misc

 filesystem: btrfs
-zram_fraction: 1.0
+zram_fraction: 2.0
 wireguard_address: 10.0.0.6
 wireguard_public_key: F2X4lMxdET35mceNtRVqSxVVbwEUVey5IjveG0yHJ0Q=