Update release-pgpool.yml

Author: cbaker6

.github/workflows/release-pgpool.yml

@@ -66,7 +66,7 @@ jobs:
     needs: docker
     runs-on: ubuntu-latest
     container:
-      image: quay.io/singularity/singularity:v3.11.4
+      image: quay.io/singularity/singularity:v4.1.0
     strategy:
       fail-fast: false
       matrix: