fix(metadata): make matchesLanguageFamily protected for subclass access

DSC-896

ItemServiceImpl extends DSpaceObjectServiceImpl and calls matchesLanguageFamily
in its getMetadata override. The method was private, causing a compile error.
Changed visibility to protected.

Author: vins01-4science

dspace-api/src/main/java/org/dspace/content/DSpaceObjectServiceImpl.java

@@ -1196,7 +1196,7 @@ private List<MetadataValue> filterByLanguage(List<MetadataValue> metadataValues,
      * @param storedLang    the language stored on the metadata value (may be {@code null})
      * @return {@code true} if the stored language satisfies the request
      */
-    private boolean matchesLanguageFamily(String requestedLang, String storedLang) {
+    protected boolean matchesLanguageFamily(String requestedLang, String storedLang) {
         if (requestedLang == null) {
             return storedLang == null;
         }