build: rev cantrip rust toolchain to nightly-1.71.0

Needed for toml_edit v0.22.5.

Change-Id: Ic6351905940484a5328a9be4757597f973b9d281

setup.sh

diff --git a/setup.sh b/setup.sh
index d2d988d..a8e58f3 100644
--- a/setup.sh
+++ b/setup.sh
@@ -60,7 +60,7 @@
 export PATH="${OUT}/host/verilator/bin:${PATH}"
 export PATH="${OUT}/host/verible/bin:${PATH}"
 
-export CANTRIP_RUST_VERSION=${CANTRIP_RUST_VERSION:-"nightly-2023-01-26"}
+export CANTRIP_RUST_VERSION=${CANTRIP_RUST_VERSION:-"nightly-2023-04-20"}
 export RENODE_PORT=1234
 
 export PYTHONPATH="${PYTHONPATH}:${ROOTDIR}/cicd/"