[OOTB] Update PostgreSQL images to use specific digests (#431)

`ootb` variant of #430

Fixes #427

Author: edeandrea

scripts/infra.sh

@@ -67,7 +67,7 @@ start_postgres() {
     --rm \
     --name ${DB_CONTAINER_NAME} \
     -p 5432:5432 \
-    ghcr.io/quarkusio/postgres-17-perf:main \
+    ghcr.io/quarkusio/postgres-17-perf@sha256:25547aa2c1a44685066f552e1c262929cf629cbc2f3a82bd18fa791a03f7cd48 \
     -c fsync=off \
     -c synchronous_commit=off \
     -c autovacuum=off \