[gnumeric] Doc fix.

[Morten Welinder <mortenw src gnome org>]

commit cbc72bc246b55d35a6c60839f69f22025f901bd1
Author: Morten Welinder <terra gnome org>
Date:   Mon Nov 26 20:43:47 2018 -0500

    Doc fix.

 src/mathfunc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/mathfunc.c b/src/mathfunc.c
index c04106dd2..e5360891a 100644
--- a/src/mathfunc.c
+++ b/src/mathfunc.c
@@ -5026,7 +5026,8 @@ gnm_agm (gnm_float a, gnm_float b)
  * @x: a number
  * @k: branch, either 0 or -1
  *
- * Returns: The arithmetic-geometric mean of @a and @b.
+ * Returns: The Lambert W function at @x.  @k is a branch number: 0
+ * for the primary branch and -1 for the alternate.
  */
 gnm_float
 gnm_lambert_w (gnm_float x, int k)