flatpak: deprecate official support

See #309

cicd/flatpak-build/Dockerfile

@@ -1,17 +0,0 @@
-FROM fedora:30
-
-LABEL maintainer robozman "https://gitlab.com/robozman"
-
-VOLUME [ "/sys/fs/cgroup", "/tmp", "/run" ]
-
-
-RUN dnf -y update && \
-    dnf install -y flatpak flatpak-builder ostree fuse wget curl elfutils dconf git bzip2 bzr python3 python3-pip && \
-    dnf clean all
-
-RUN flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
-
-RUN flatpak install -y org.gnome.Platform//3.38 && \
-    flatpak install -y org.gnome.Sdk//3.38
-
-RUN pip3 install requirements-parser

cicd/publish-gitlab-release.sh

@@ -48,29 +48,6 @@ if [[ "${milestone}" != "" ]]; then
     milestones=",\"milestones\":[\"${milestone}\"]"
 fi
 
-# Determine whether or not to include the Flatpak build.
-set +e
-failed=$(curl \
-    --header "PRIVATE-TOKEN: ${RELEASE_PUBLISH_TOKEN}" \
-    --request GET \
-    "${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/pipelines/${CI_PIPELINE_ID}/jobs?scope[]=failed" \
-    | grep '"name":"build_flatpak"')
-set -e
-
-assets=""
-if [[ $failed == "" ]]; then
-    assets=",
-    \"assets\": {
-        \"links\": [
-            {
-                \"name\": \"sublime-music-${CI_COMMIT_TAG}.flatpak\",
-                \"url\": \"${CI_PROJECT_URL}/-/jobs/artifacts/${CI_COMMIT_TAG}/raw/flatpak/sublime-music.flatpak?job=build_flatpak\"
-            }
-        ]
-    }
-    "
-fi
-
 url="${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/releases"
 data="
 {