CI: drop setup of snd-dummy module

Apparently even when loading the snd-dummy kernel module, the
CI tests for the sounds feature in test_sound.vim are already skipped.

So let's just remove all of this (even so we may loose a bit of coverage
information here).

closes: #16391

Signed-off-by: Philip H. <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: pheiduck

.github/workflows/ci.yml

@@ -215,21 +215,6 @@ jobs:
           sudo usermod -a -G audio "${USER}"
           sudo bash ci/setup-xvfb.sh
 
-      - name: Set up snd-dummy
-        if: (!(contains(matrix.extra, 'unittests') || contains(matrix.extra, 'vimtags')))
-        env:
-          DEST_DIR: ${{ env.TMPDIR }}/linux-modules-extra-${{ env.LINUX_VERSION }}
-        uses: tecolicom/actions-use-apt-tools@main
-        with:
-          tools: linux-modules-extra-${{ env.LINUX_VERSION }}
-          path: "${DEST_DIR}"
-
-      - name: modprobe snd-dummy
-        if: (!(contains(matrix.extra, 'unittests') || contains(matrix.extra, 'vimtags')))
-        run: |
-          sudo depmod --verbose
-          sudo modprobe --verbose snd-dummy || true
-
       - name: Check autoconf
         if: contains(matrix.extra, 'unittests')
         run: |