ci: skip downstream sanitize test for now

pending a fix for #3348

.github/workflows/downstream.yml

@@ -20,9 +20,11 @@ on:
 jobs:
   downstream:
     name: downstream-${{matrix.name}}
+    continue-on-error: ${{ matrix.ok_to_fail }}
     strategy:
       fail-fast: false
       matrix:
+        ok_to_fail: [false]
         include:
           - url: https://github.com/flavorjones/loofah
             name: loofah
@@ -36,6 +38,7 @@ jobs:
             name: sanitize
             command: "bundle exec rake test"
             ruby: "3.3"
+            ok_to_fail: true # pending a fix for https://github.com/sparklemotion/nokogiri/pull/3348
           - url: https://github.com/ebeigarts/signer
             name: signer
             command: "bundle exec rake spec"