Update src/hb-ot-math.cc

Co-Authored-By: Khaled Hosny <khaledhosny@eglug.org>
diff --git a/src/hb-ot-math.cc b/src/hb-ot-math.cc
index 99ce744..6883852 100644
--- a/src/hb-ot-math.cc
+++ b/src/hb-ot-math.cc
@@ -97,7 +97,7 @@
  * Fetches an italics-correction value (if one exists) for the specified
  * glyph index.
  *
- * Return value: the italics correction of the glyph or 0
+  * Return value: the italics correction of the glyph or zero
  *
  * Since: 1.3.3
  **/