patch 8.0.0206: test coverage for :retab insufficient

Problem:    Test coverage for :retab insufficient.
Solution:   Add test for :retab. (Dominique Pelle, closes #1391)
diff --git a/src/version.c b/src/version.c
index 766f989..f3c4a4b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    206,
+/**/
     205,
 /**/
     204,