Upgrade Rust toolchain to `nightly-2024-03-21` #4944

	# Copyright Kani Contributors
	# SPDX-License-Identifier: Apache-2.0 OR MIT

	# 1. Checks licenses for allowed license.
	# 2. Checks Rust-Sec registry for security advisories.

	name: Cargo Audit
	on:
	pull_request:
	push:
	# Run on changes to branches but not tags.
	branches:
	- '**'

	jobs:
	audit:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	- uses: EmbarkStudios/cargo-deny-action@v1
	with:
	arguments: --all-features --workspace
	command-arguments: -s

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