refactor: move max failed batches configuration to retry section; clean up unused error handling code

internal/app/custom_errors/backoff.go

@@ -1,7 +1,6 @@
 package custom_errors
 
 import (
-	"context"
 	"math/rand"
 	"time"
 )
@@ -40,22 +39,3 @@ func ComputeBackoffDelay(retryCounter int, baseDelayMs int, maxDelayMs int, maxJ
 
 	return delay
 }
-
-func requeueWithBackoff(ctx context.Context, delay time.Duration, enqueue func()) {
-	if delay <= 0 {
-		enqueue()
-		return
-	}
-
-	go func() {
-		timer := time.NewTimer(delay)
-		defer timer.Stop()
-
-		select {
-		case <-ctx.Done():
-			return
-		case <-timer.C:
-			enqueue()
-		}
-	}()
-}