Remove AppImage build

After testing, I've concluded that the AppImage build is not good enough
foir general usage. It has very long startup time by default, and the
parameters that allow AppImage files to be reused between app restarts
result in 500mb of data stored in /tmp, which is in RAM on most
systems..

Hopefully pkger with native packages should be good enough, even
considering gtk4 not being available everywhere

AppImageBuilder.yml

@@ -1,55 +0,0 @@
-# appimage-builder recipe see https://appimage-builder.readthedocs.io for details
-version: 1
-script: |
-  rm AppDir -r | true
-  make build-release
-  make install DESTDIR=AppDir/usr
-AppDir:
-  path: /home/ilya/dev/LACT/AppDir
-  app_info:
-    id: io.github.lact-linux
-    name: LACT
-    icon: io.github.lact-linux
-    version: latest
-    exec: usr/bin/lact
-    exec_args: $@
-  pacman:
-    include:
-      - gtk4
-      - wayland
-      - hwdata
-    exclude:
-      - llvm
-      - llvm-libs
-      - mesa
-  files:
-    include:
-    - /lib64/ld-linux-x86-64.so.2
-    exclude:
-    - usr/share/man
-    - usr/share/doc/*/README.*
-    - usr/share/doc/*/changelog.*
-    - usr/share/doc/*/NEWS.*
-    - usr/share/doc/*/TODO.*
-    - usr/include
-    - usr/share/locale
-    - etc
-  test:
-    fedora-30:
-      image: appimagecrafters/tests-env:fedora-30
-      command: ./AppRun help
-    debian-stable:
-      image: appimagecrafters/tests-env:debian-stable
-      command: ./AppRun help
-    archlinux-latest:
-      image: appimagecrafters/tests-env:archlinux-latest
-      command: ./AppRun help
-    centos-7:
-      image: appimagecrafters/tests-env:centos-7
-      command: ./AppRun help
-    ubuntu-xenial:
-      image: appimagecrafters/tests-env:ubuntu-xenial
-      command: ./AppRun help
-AppImage:
-  arch: x86_64
-  update-information: guess