Remove/address some TODOs (#6923)

ledger/src/bank_forks.rs

@@ -165,7 +165,6 @@ impl BankForks {
         bank
     }
 
-    // TODO: really want to kill this...
     pub fn working_bank(&self) -> Arc<Bank> {
         self.working_bank.clone()
     }

ledger/src/blocktree_processor.rs

@@ -428,7 +428,6 @@ fn process_next_slots(
     }
 
     // Reverse sort by slot, so the next slot to be processed can be popped
-    // TODO: remove me once leader_scheduler can hang with out-of-order slots?
     pending_slots.sort_by(|a, b| b.0.cmp(&a.0));
     Ok(())
 }