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

This reverts commit 732f06b4ee2153bd8dbd0b8dad2c3a291f9b373a.

Reason for revert: apps on nexus hw fail

Change-Id: I3036680113f26826ebed1c0686bfa30bfbd4aef4

setup.sh

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