ci: stop ignoring Amazon Linux 2

With the latest change in SYS constants, Amazon Linux 2 should
work again.

Author: rfjakob

.github/workflows/ci.yml

@@ -52,8 +52,6 @@ jobs:
           git config --global --add safe.directory /work # Fix for: fatal: detected dubious ownership in repository at '/work'
           make
           make test
-      # Fails because kernel is too old for SYS_pidfd_open
-      continue-on-error: true
     - run: git clean -dxff
 
     - name: Build in Oracle Linux 7 (similar to RHEL 7, CentOS 7)