patch 8.2.2568: second time a preview popup is opened highlight is not set

Problem:    Second time a preview popup is opened highlight is not set.
            (Gabriel Dupras)
Solution:   Apply 'previewpopup' after getting the file. (closes #7928)
diff --git a/src/version.c b/src/version.c
index 879931d..da9328c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2568,
+/**/
     2567,
 /**/
     2566,