Use 9 for max blobs when sizing BlobCache (#8222)

Supports Pectra EIP-7691

Signed-off-by: Simon Dudley <simon.dudley@consensys.net>

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/transactions/BlobCache.java

@@ -34,7 +34,8 @@ public class BlobCache {
   public BlobCache() {
     this.cache =
         Caffeine.newBuilder()
-            .maximumSize(6 * 32 * 3L) // 6 blobs max per 32 slots per 3 epochs
+            .maximumSize(
+                9 * 32 * 3L) // 9 blobs max (since Prague EIP-7691) per 32 slots per 3 epochs
             .expireAfterWrite(
                 3 * 32 * 12L, TimeUnit.SECONDS) // 3 epochs of 32 slots which take 12 seconds each.
             .build();