Remove unnecessary @SuppressWarnings

Change-Id: Ic7b8494713d59574ee8f064a5c1042b48aedf012

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/FileSender.java

@@ -220,7 +220,6 @@ final class FileSender {
 		return true;
 	}
 
-	@SuppressWarnings("unchecked")
 	private static Enumeration<String> getRange(final HttpServletRequest req) {
 		return req.getHeaders(HDR_RANGE);
 	}