[LyX/master] Add forgotten case

[Juergen Spitzmueller]

commit 0ab6a5c6d6321b1b5b29fa173d837e1d2930bd59
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Sun Feb 5 09:34:04 2023 +0100

    Add forgotten case
---
 lib/lyx2lyx/lyx_2_4.py |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/lib/lyx2lyx/lyx_2_4.py b/lib/lyx2lyx/lyx_2_4.py
index d3646dc..7c11957 100644
--- a/lib/lyx2lyx/lyx_2_4.py
+++ b/lib/lyx2lyx/lyx_2_4.py
@@ -4744,6 +4744,7 @@ ack_layouts_old = {
     "egs" : "Acknowledgements",# + Acknowledgement
     "elsart" : "Acknowledegment",
     "isprs" : "Acknowledgements",
+    "iucr" : "Acknowledgements",
     "kluwer" : "Acknowledgements",
     "svglobal3" : "Acknowledgements",
     "svglobal" : "Acknowledgement",