revert fast path validation

Signed-off-by: Alex Chi Z <chi@neon.tech>

pageserver/src/deletion_queue/validator.rs

@@ -304,15 +304,6 @@ where
     async fn flush(&mut self) -> Result<(), DeletionQueueError> {
         tracing::debug!("Flushing with {} pending lists", self.pending_lists.len());
 
-        // Fast path to skip validation if we do not have anything to flush.
-        if self.pending_lists.is_empty()
-            && self.validated_lists.is_empty()
-            && self.pending_key_count == 0
-        {
-            // Fast path: nothing to do
-            return Ok(());
-        }
-
         // Issue any required generation validation calls to the control plane
         self.validate().await?;