Ubuntu 21 tests are failing entirely. apt-update does not work on an impish vm, either

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

.github/workflows/test.yml

@@ -43,7 +43,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        distro: [debian_10, debian_11, ubuntu_18, ubuntu_20, ubuntu_21, ubuntu_22, centos_7, centos_8, fedora_34]
+        distro: [debian_10, debian_11, ubuntu_18, ubuntu_20, ubuntu_22, centos_7, centos_8, fedora_34]
     env:
       DISTRO: ${{matrix.distro}}
     steps:

test/_ubuntu_21.Dockerfile

@@ -1,18 +0,0 @@
-FROM buildpack-deps:impish-scm
-
-ENV GITDIR /etc/.pihole
-ENV SCRIPTDIR /opt/pihole
-
-RUN mkdir -p $GITDIR $SCRIPTDIR /etc/pihole
-ADD . $GITDIR
-RUN cp $GITDIR/advanced/Scripts/*.sh $GITDIR/gravity.sh $GITDIR/pihole $GITDIR/automated\ install/*.sh $SCRIPTDIR/
-ENV PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$SCRIPTDIR
-ENV DEBIAN_FRONTEND=noninteractive
-
-RUN true && \
-    chmod +x $SCRIPTDIR/*
-
-ENV SKIP_INSTALL true
-ENV OS_CHECK_DOMAIN_NAME dev-supportedos.pi-hole.net
-
-#sed '/# Start the installer/Q' /opt/pihole/basic-install.sh > /opt/pihole/stub_basic-install.sh && \

test/tox.ubuntu_21.ini

@@ -1,8 +0,0 @@
-[tox]
-envlist = py38
-
-[testenv]
-whitelist_externals = docker
-deps = -rrequirements.txt
-commands = docker build -f _ubuntu_21.Dockerfile -t pytest_pihole:test_container ../
-           pytest {posargs:-vv -n auto} ./test_any_automated_install.py ./test_any_utils.py