build: rev cantrip rust toolchain to the nightly equivalent of stable 1.74.1

Change-Id: Iee63d4f84b77358aed9ec1de0e7cb55567cf57b3

setup.sh

diff --git a/setup.sh b/setup.sh
index d2d988d..5ed2233 100644
--- a/setup.sh
+++ b/setup.sh
@@ -60,7 +60,9 @@
 export PATH="${OUT}/host/verilator/bin:${PATH}"
 export PATH="${OUT}/host/verible/bin:${PATH}"
 
-export CANTRIP_RUST_VERSION=${CANTRIP_RUST_VERSION:-"nightly-2023-01-26"}
+# NB: this corresponds to stable 1.74.1; approximated with rustc --version:
+# rustc 1.74.1 (a28077b28 2023-12-04)
+export CANTRIP_RUST_VERSION=${CANTRIP_RUST_VERSION:-"nightly-2023-12-04"}
 export RENODE_PORT=1234
 
 export PYTHONPATH="${PYTHONPATH}:${ROOTDIR}/cicd/"