CI: do not print tar filenames

Redirect tar output to /dev/null as we only care about the exit code
here, not what it prints to stdout.

extras/ci/gitlab-ci.yml

@@ -10,7 +10,7 @@ default:
     after_script:
         - export VLC_CONTRIB_SHA="$(extras/ci/get-contrib-sha.sh)"
         - mv contrib/vlc-contrib-*.tar.bz2 contrib/vlc-contrib-${TRIPLET}-${VLC_CONTRIB_SHA}.tar.bz2 2>/dev/null || true
-        - cd contrib && find . -maxdepth 1 -type f -name "vlc-contrib-*-${VLC_CONTRIB_SHA}.tar.bz2" -exec sh -c 'tar tvf "$0" && shasum -a 512 "$0" | tee SHA512SUM' "{}" \;
+        - cd contrib && find . -maxdepth 1 -type f -name "vlc-contrib-*-${VLC_CONTRIB_SHA}.tar.bz2" -exec sh -c 'tar tf "$0" > /dev/null && shasum -a 512 "$0" | tee SHA512SUM' "{}" \;
     interruptible: true
 
 variables: