fix: op-challenger move.go cli command wasn't cancellable (#11716)

op-challenger/cmd/move.go

 package main
 
 import (
-	"context"
 	"fmt"
 
 	"github.com/ethereum-optimism/optimism/op-challenger/flags"
@@ -70,7 +69,7 @@ func Move(ctx *cli.Context) error {
 		return fmt.Errorf("either attack or defense flag must be set")
 	}
 
-	rct, err := txMgr.Send(context.Background(), tx)
+	rct, err := txMgr.Send(ctx.Context, tx)
 	if err != nil {
 		return fmt.Errorf("failed to send tx: %w", err)
 	}