patch 8.1.0926: no test for :wnext, :wNext and :wprevious

Problem:    No test for :wnext, :wNext and :wprevious.
Solution:   Add a test. (Dominique Pelle, closes #3963)
diff --git a/src/version.c b/src/version.c
index 567e870..1451697 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    926,
+/**/
     925,
 /**/
     924,