Remove support for End Of Life (EOL) Fedora 22

Fedora 22 reaches its EOL on 19-JUL-2016[1].  Remove it as
officially supported distribution.

The current two supported Fedora distributions are Fedora 23 and Fedora
24.  (Change Ia4a58de4973ef228735c48b33453a0562dc65258 already added
support for Fedora 24.)

[1] https://fedoramagazine.org/fedora-22-end-of-life-2016-july/

Change-Id: I5b4e1ddb6165a9065e80e84175246678a7356f18
diff --git a/stack.sh b/stack.sh
index 5a5a040..4cace9d 100755
--- a/stack.sh
+++ b/stack.sh
@@ -185,7 +185,7 @@
 
 # Warn users who aren't on an explicitly supported distro, but allow them to
 # override check and attempt installation with ``FORCE=yes ./stack``
-if [[ ! ${DISTRO} =~ (trusty|wily|xenial|7.0|wheezy|sid|testing|jessie|f22|f23|f24|rhel7|kvmibm1) ]]; then
+if [[ ! ${DISTRO} =~ (trusty|wily|xenial|7.0|wheezy|sid|testing|jessie|f23|f24|rhel7|kvmibm1) ]]; then
     echo "WARNING: this script has not been tested on $DISTRO"
     if [[ "$FORCE" != "yes" ]]; then
         die $LINENO "If you wish to run this script anyway run with FORCE=yes"