Fix CacheStats forward declaration to match struct definition.

Aligns the forward declaration with the struct definition to silence -Wmismatched-tags.

Assisted-by: Cursor:Composer-2.5 CursorAI

Author: apeters1971

src/XrdApps/XrdClJournalCachePlugin/file/CacheStats.hh

@@ -447,5 +447,5 @@ struct CacheStats {
       run();
     }
   }
-}; // class CacheStats
+}; // struct CacheStats
 } // namespace JournalCache

src/XrdApps/XrdClJournalCachePlugin/file/XrdClJournalCacheFile.hh

@@ -52,7 +52,7 @@
 /*----------------------------------------------------------------------------*/
 
 namespace JournalCache {
-class CacheStats;
+struct CacheStats;
 }
 
 namespace XrdCl {