Remove flatpak from main repo

melonDS is on flathub and the flatpak package is maintained on a seperate repository.

flatpak/net.kuribo64.melonDS.yml

@@ -1,29 +0,0 @@
----
-app-id: net.kuribo64.melonDS
-runtime: org.freedesktop.Platform
-runtime-version: '18.08'
-sdk: org.freedesktop.Sdk
-command: melonDS
-finish-args:
-  - "--share=ipc"
-  - "--socket=x11"
-  - "--socket=pulseaudio"
-  - "--share=network"
-  - "--device=all"
-  - "--filesystem=home"
-modules:
-  - name: libpcap
-    sources:
-      - type: archive
-        url: http://www.tcpdump.org/release/libpcap-1.9.0.tar.gz
-        sha256: 2edb88808e5913fdaa8e9c1fcaf272e19b2485338742b5074b9fe44d68f37019
-
-  - name: melonds
-    buildsystem: cmake-ninja
-    sources:
-      - type: git
-        url: https://github.com/Arisotura/melonDS.git
-        branch: master
-    post-install:
-      - "desktop-file-install --dir=/app/share/applications net.kuribo64.melonDS.desktop"
-      - "install -D icon/melon_256x256.png /app/share/icons/hicolor/256x256/apps/net.kuribo64.melonDS.png"