packaging: drop "support" for unsupported Fedora versions stable

packaging: drop "support" for unsupported Fedora versions

Fedora 31 has just been released, and Fedora 29 will be EOL in a month. Don't
spend any time thinking about dead stuff.

--- a/Makefile	Wed Oct 30 16:39:18 2019 -0400
+++ b/Makefile	Thu Oct 31 11:53:11 2019 +0100
@@ -189,9 +189,6 @@
   docker-centos7 \
   docker-debian-jessie \
   docker-debian-stretch \
-  docker-fedora20 \
-  docker-fedora21 \
-  docker-fedora28 \
   docker-fedora29 \
   docker-ubuntu-trusty \
   docker-ubuntu-trusty-ppa \
@@ -201,9 +198,6 @@
   docker-ubuntu-artful-ppa \
   docker-ubuntu-bionic \
   docker-ubuntu-bionic-ppa \
-  fedora20 \
-  fedora21 \
-  fedora28 \
   fedora29 \
   linux-wheels \
   linux-wheels-x86_64 \

--- a/contrib/packaging/Makefile	Wed Oct 30 16:39:18 2019 -0400
+++ b/contrib/packaging/Makefile	Thu Oct 31 11:53:11 2019 +0100
@@ -12,9 +12,6 @@
   disco
 
 FEDORA_RELEASES := \
-  20 \
-  21 \
-  28 \
   29
 
 CENTOS_RELEASES := \

--- a/contrib/packaging/docker/fedora20	Wed Oct 30 16:39:18 2019 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,15 +0,0 @@
-FROM fedora:20
-
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
-
-RUN yum install -y \
-	gcc \
-	gettext \
-	make \
-	python-devel \
-	python-docutils \
-	rpm-build
-
-# For creating repo meta data
-RUN yum install -y createrepo

--- a/contrib/packaging/docker/fedora21	Wed Oct 30 16:39:18 2019 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,15 +0,0 @@
-FROM fedora:21
-
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
-
-RUN yum install -y \
-	gcc \
-	gettext \
-	make \
-	python-devel \
-	python-docutils \
-	rpm-build
-
-# For creating repo meta data
-RUN yum install -y createrepo

--- a/contrib/packaging/docker/fedora28	Wed Oct 30 16:39:18 2019 -0400
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,15 +0,0 @@
-FROM fedora:28
-
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
-
-RUN dnf install -y \
-	gcc \
-	gettext \
-	make \
-	python-devel \
-	python-docutils \
-	rpm-build
-
-# For creating repo meta data
-RUN dnf install -y createrepo