patch 9.0.0353: missing entry in switch

Problem:    Missing entry in switch.
Solution:   Add ISN_ECHOWINDOW.
diff --git a/src/vim9instr.c b/src/vim9instr.c
index f20d993..a13516b 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -2245,6 +2245,7 @@
 	case ISN_ECHOCONSOLE:
 	case ISN_ECHOERR:
 	case ISN_ECHOMSG:
+	case ISN_ECHOWINDOW:
 	case ISN_ENDTRY:
 	case ISN_EXECCONCAT:
 	case ISN_EXECUTE: