Add allow deprecated to get_max_age (#8714)

* Add allow deprecated to get_max_age

* Update accounts-db/src/blockhash_queue.rs

Co-authored-by: Trent Nelson <490004+t-nelson@users.noreply.github.com>

---------

Co-authored-by: Trent Nelson <490004+t-nelson@users.noreply.github.com>

accounts-db/src/blockhash_queue.rs

@@ -141,6 +141,7 @@ impl BlockhashQueue {
         note = "Please use `solana_clock::MAX_PROCESSING_AGE`"
     )]
     pub fn get_max_age(&self) -> usize {
+        #[allow(deprecated)]
         self.max_age
     }
 }