Add Fedora 34 support

* update the support distro filter

* don't install xinetd which doesn't exist in F34 any more.  I think
  there is probably a bit more to do with swift ring-server but that
  can be a problem for another time.

* remove old F31 workaround

Change-Id:If2f74f146a166b9721540aaf3f1f9fce3030525c
diff --git a/stack.sh b/stack.sh
index c439a72..47d6dc7 100755
--- a/stack.sh
+++ b/stack.sh
@@ -227,7 +227,7 @@
 
 # Warn users who aren't on an explicitly supported distro, but allow them to
 # override check and attempt installation with ``FORCE=yes ./stack``
-SUPPORTED_DISTROS="focal|f31|f32|opensuse-15.2|opensuse-tumbleweed|rhel8"
+SUPPORTED_DISTROS="focal|f34|opensuse-15.2|opensuse-tumbleweed|rhel8"
 
 if [[ ! ${DISTRO} =~ $SUPPORTED_DISTROS ]]; then
     echo "WARNING: this script has not been tested on $DISTRO"