patch 8.2.2531: Vim9: the :k command is obscure

Problem:    Vim9: the :k command is obscure.
Solution:   Disallow using :k, can use :mark instead. (closes #7874)
diff --git a/src/vim9script.c b/src/vim9script.c
index d40104c..751d8fb 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -95,6 +95,7 @@
 	    case CMD_append:
 	    case CMD_change:
 	    case CMD_insert:
+	    case CMD_k:
 	    case CMD_t:
 	    case CMD_xit:
 		semsg(_(e_command_not_supported_in_vim9_script_missing_var_str), eap->cmd);