CI: don't try to fetch repos of deleted apps.

--diff-filter=d excludes (because of the lowercase letter) deleted
files.

.gitlab-ci.yml

@@ -14,7 +14,7 @@ lint:
     - if [ "$CI_PROJECT_NAMESPACE" != "fdroid" ]; then
         git fetch https://gitlab.com/fdroid/fdroiddata;
         test -d build || mkdir build;
-        for f in `git diff --name-only FETCH_HEAD...HEAD`; do
+        for f in `git diff --name-only --diff-filter=d FETCH_HEAD...HEAD`; do
            appid=`echo $f | sed -n -e 's,^metadata/\([^/][^/]*\)\.txt,\1,p'
                                    -e 's,^metadata/\([^/][^/]*\)\.yml,\1,p'`;
            export CHANGED="$CHANGED $appid";