patch 8.1.2286: using border highlight in popup window leaks memory

Problem:    Using border highlight in popup window leaks memory.
Solution:   Free memory before overwriting. (Dominique Pelle, closes #5203)
diff --git a/src/version.c b/src/version.c
index 823d4d8..ab75ea7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2286,
+/**/
     2285,
 /**/
     2284,