Remove broken flatpak builds for now

.github/workflows/build-on-pr.yaml

@@ -30,10 +30,7 @@ jobs:
       - name: Install builder dependencies
         shell: bash
         run: |
-          sudo apt install flatpak -y
-          sudo apt install flatpak-builder -y
           sudo apt install elfutils -y
-          flatpak remote-add --if-not-exists --user flathub https://flathub.org/repo/flathub.flatpakrepo
           git config --global --add protocol.file.allow always
       - name: Build the app
         shell: bash