Release process: keep more IUKs to be nicer with people who don't use Tails often.

Currently we use only 13G out of the 30G our mirrors are supposed to have
so we can afford it.

wiki/src/contribute/release_process.mdwn

@@ -1364,14 +1364,14 @@ this, and skip what does not make sense for a RC.
      `ssh bittorrent.lizard transmission-remote -t "${PREVIOUS_VERSION_TRANSMISSION_ID:?}" --remove-and-delete`
 1. Remove any remaining RC for the just-published release from
    the mirrors.
-1. Remove IUKs that are more than 6 months old from
+1. Remove IUKs that are more than 9 months old from
    `/{stable,alpha}/iuk` on the rsync server:
    - first check that it's not going to remove anything we want to keep:
 
          ssh rsync.lizard /bin/sh -c \
              \"find /srv/rsync/tails/tails/alpha  \
                     /srv/rsync/tails/tails/stable \
-                    -type f -name '*.iuk' -mtime '+183' \
+                    -type f -name '*.iuk' -mtime '+270' \
                     -not -name '*~test_*~test.iuk' -ls \
              \"
 
@@ -1380,7 +1380,7 @@ this, and skip what does not make sense for a RC.
          ssh rsync.lizard /bin/sh -c \
              \"find /srv/rsync/tails/tails/alpha  \
                     /srv/rsync/tails/tails/stable \
-                    -type f -name '*.iuk' -mtime '+183' \
+                    -type f -name '*.iuk' -mtime '+270' \
                     -not -name '*~test_*~test.iuk' -delete \
              \"