use existing getUrlsCacheKey method

the getUrls where recreating manually the cache key wherease there already is a method to do that ...

src/StaticCaching/Cachers/AbstractCacher.php

@@ -139,10 +139,10 @@ public function cacheDomain($domain = null)
  public function getUrls($domain = null)
  {
  $domain = $domain ?: $this->getBaseUrl();
-
- $domain = $this->makeHash($domain);
-
- return collect($this->cache->get($this->normalizeKey($domain.'.urls'), []));
+ 
+ $key = $this->getUrlsCacheKey($domain);
+ 
+ return collect($this->cache->get($key, []));
  }
 
  /**