Use core 2.27.0 in valgrind CI as well (#786)

Author: johnkerl

.github/workflows/valgrind.yaml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        tag: [ release-2.25, release-2.26, dev ]
+        tag: [ release-2.25, release-2.26, release-2.27, dev ]
 
     steps:
     - name: Checkout