Update CI.

Author: gkellogg

.github/workflows/ci.yml

@@ -15,6 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       CI: true
+      ALLOW_FAILURES: ${{ endsWith(matrix.ruby, 'head') || matrix.ruby == 'jruby' }}
     strategy:
       fail-fast: false
       matrix:
@@ -23,7 +24,7 @@ jobs:
           - 2.5
           - 2.6
           - 2.7
-          #- ruby-head # net-http-persistent
+          - ruby-head
           - jruby
     steps:
       - name: Clone repository
@@ -35,5 +36,5 @@ jobs:
       - name: Install dependencies
         run: bundle install --jobs 4 --retry 3
       - name: Run tests
-        run: bundle exec rspec spec
+        run: ruby --version; bundle exec rspec spec || $ALLOW_FAILURES