Amend HBASE-26353 Support loadable dictionaries in hbase-compression-zstd (#3787)

Resolve a new spotbugs warning in DictionaryCache

Signed-off-by: Andrew Purtell <apache.org>

Author: apurtell

hbase-common/src/main/java/org/apache/hadoop/hbase/io/compress/DictionaryCache.java

@@ -46,7 +46,7 @@ public final class DictionaryCache {
   public static final String RESOURCE_SCHEME = "resource://";
 
   private static final Logger LOG = LoggerFactory.getLogger(DictionaryCache.class);
-  private static LoadingCache<String, byte[]> CACHE;
+  private static volatile LoadingCache<String, byte[]> CACHE;
 
   private DictionaryCache() { }