patch 8.2.1543: Vim9: test with invalid SID is skipped in the GUI

Problem:    Vim9: test with invalid SID is skipped in the GUI.
Solution:   Read the CTRL-C that feedkeys() put in typeahead.
diff --git a/src/version.c b/src/version.c
index 1a66eb6..8eaf484 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1543,
+/**/
     1542,
 /**/
     1541,