patch 8.1.0047: no completion for :unlet $VAR

Problem:    No completion for :unlet $VAR.
Solution:   Add completion. (Jason Franklin)
diff --git a/src/version.c b/src/version.c
index 2ce060c..d290fda 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    47,
+/**/
     46,
 /**/
     45,