Replace REPLACEME's left out of 2.4.0

https://github.com/harfbuzz/harfbuzz/issues/1641

src/hb-directwrite.cc

diff --git a/src/hb-directwrite.cc b/src/hb-directwrite.cc
index 137cd56..cbf04a8 100644
--- a/src/hb-directwrite.cc
+++ b/src/hb-directwrite.cc
@@ -918,7 +918,7 @@
 /**
  * hb_directwrite_face_create:
  * @font_face:
- * Since: REPLACEME
+ * Since: 2.4.0
  **/
 hb_face_t *
 hb_directwrite_face_create (IDWriteFontFace *font_face)