Marks Bank::unfreeze_for_ledger_tool() as dcou (#3160)

runtime/src/bank.rs

@@ -2911,6 +2911,7 @@ impl Bank {
     }
 
     // dangerous; don't use this; this is only needed for ledger-tool's special command
+    #[cfg(feature = "dev-context-only-utils")]
     pub fn unfreeze_for_ledger_tool(&self) {
         self.freeze_started.store(false, Relaxed);
     }