Add missing @since tags for new API

These methods were added after 4.11 so strictly speaking they violate
semantic versioning since new API requires increasing the minor version
number. Hence pretend these methods were introduced in 5.0

Change-Id: I7793ead16577dc1f2ddea09ba6b055103c783555
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectIdSerializer.java

@@ -108,6 +108,7 @@ public class ObjectIdSerializer {
 	 *            the object id to serialize; never null
 	 * @throws IOException
 	 *             the stream writing failed
+	 * @since 5.0
 	 */
 	public static void writeWithoutMarker(OutputStream out, @NonNull AnyObjectId id)
 			throws IOException {
@@ -147,6 +148,7 @@ public class ObjectIdSerializer {
 	 * @return the object id; never null
 	 * @throws IOException
 	 *             there was an error reading the stream
+	 * @since 5.0
 	 */
 	@NonNull
 	public static ObjectId readWithoutMarker(InputStream in) throws IOException {