fix: remove nix and flatpak support

.github/workflows/build.yml

@@ -630,71 +630,4 @@ jobs:
         shell: msys2 {0}
         run: |
           ccache -s
-
-  flatpak:
-    runs-on: ubuntu-latest
-    container:
-      image: bilelmoussaoui/flatpak-github-actions:kde-6.7
-      options: --privileged
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        if: inputs.build_type == 'Debug'
-        with:
-          submodules: "true"
-      - name: Build Flatpak (Linux)
-        if: inputs.build_type == 'Debug'
-        uses: flatpak/flatpak-github-actions/flatpak-builder@v6
-        with:
-          bundle: "Prism Launcher.flatpak"
-          manifest-path: flatpak/org.prismlauncher.PrismLauncher.yml
-
-  nix:
-    name: Nix (${{ matrix.system }})
-
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - os: ubuntu-22.04
-            system: x86_64-linux
-
-          - os: macos-13
-            system: x86_64-darwin
-
-          - os: macos-14
-            system: aarch64-darwin
-
-    runs-on: ${{ matrix.os }}
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Install Nix
-        uses: cachix/install-nix-action@v30
-
-        # For PRs
-      - name: Setup Nix Magic Cache
-        uses: DeterminateSystems/magic-nix-cache-action@v8
-
-        # For in-tree builds
-      - name: Setup Cachix
-        uses: cachix/cachix-action@v15
-        with:
-          name: prismlauncher
-          authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
-
-      - name: Run flake checks
-        run: |
-          nix flake check --print-build-logs --show-trace
-
-      - name: Build debug package
-        if: ${{ inputs.build_type == 'Debug' }}
-        run: |
-          nix build --print-build-logs .#prismlauncher-debug
-
-      - name: Build release package
-        if: ${{ inputs.build_type != 'Debug' }}
-        run: |
-          nix build --print-build-logs .#prismlauncher
+