build-system: stop using openSUSE Tumbleweed

The docker container for Tumbleweed has been broken for a while now.
Given the Hirsuite gives us Qt 5.15 testing, I guess it makes sense to
drop Tumbleweed for now.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

.github/workflows/linux-tumbleweed-qt-latest.yml

@@ -1,53 +0,0 @@
-name: openSUSE/Tumbleweed / Qt latest--
-on:
-  push:
-    branches:
-    - master
-  pull_request:
-    branches:
-    - master
-
-jobs:
-  buildOpenSUSElatest:
-    runs-on: ubuntu-latest
-    container:
-      image: opensuse/tumbleweed:latest
-
-    steps:
-    - name: checkout sources
-      uses: actions/checkout@v1
-
-    - name: get container ready for build
-      run: |
-        echo "--------------------------------------------------------------"
-        echo "update distro and install dependencies"
-        zypper -n install git gcc-c++ make autoconf automake libtool cmake libzip-devel \
-        libxml2-devel libxslt-devel sqlite3-devel libusb-1_0-devel \
-        libqt5-linguist-devel libqt5-qttools-devel libQt5WebKitWidgets-devel \
-        libqt5-qtbase-devel libQt5WebKit5-devel libqt5-qtsvg-devel \
-        libqt5-qtscript-devel libqt5-qtdeclarative-devel \
-        libqt5-qtconnectivity-devel libqt5-qtlocation-devel libcurl-devel \
-        libQt5QuickControls2-devel bluez-devel \
-        which libgit2-devel libssh2-devel libmtp-devel
-
-# if we want to run the tests below, add    xvfb-run
-
-    - name: build Subsurface
-      run: |
-        echo "--------------------------------------------------------------"
-        echo "building all three binaries"
-
-        # now build the desktop version (including WebKit), mobile and downloader
-        # the mobile build needs git setup to apply the Kirigami changes
-        git config --global user.email "ci@subsurface-divelog.org"
-        git config --global user.name "Subsurface CI"
-        cd ..
-        bash -e -x subsurface/scripts/build.sh -all -build-with-webkit
-
-# let's not run the tests... to do that, we need to install 'xvfb-run' above
-#   - name: test desktop build
-#     run: |
-#       echo "--------------------------------------------------------------"
-#       echo "running tests for desktop"
-#       cd build
-#       xvfb-run --auto-servernum make check