Reduce storage size to 256Mi in pgbackrest-restore test

Author: sfc-gh-jmckulka

testing/chainsaw/e2e/pgbackrest-restore/chainsaw-test.yaml

@@ -17,7 +17,7 @@ spec:
         connect: { name: PGCONNECT_TIMEOUT, value: '5' }
 
     - name: volume
-      value: { accessModes: [ReadWriteOnce], resources: { requests: { storage: 1Gi } } }
+      value: { accessModes: [ReadWriteOnce], resources: { requests: { storage: 256Mi } } }
 
     - name: postgrescluster
       value: