Remove unstable gate for `core::error::Error` impls #3251

	name: Developer Productivity
	on:
	merge_group:
	push:
	pull_request:
	jobs:
	# Job to run change detection
	changes:
	runs-on: ubuntu-latest
	# Set job outputs to values from filter step.
	outputs:
	nix-src: ${{ steps.filter.outputs.nix-src }}
	steps:
	- name: Checkout sources
	uses: actions/checkout@v4
	- uses: dorny/paths-filter@v3
	id: filter
	with:
	filters: \|
	nix-src:
	- 'nix/**'
	- 'shell.nix'
	# This is a convenience test to verify that the toolchain provided by
	# shell.nix is valid and can build + run the integration test.
	#
	# It only runs if the "nix-src" output of the "changes" job is true.
	nix_shell_toolchain:
	name: "Nix toolchain: `cargo xtask run` works"
	needs: changes
	if: ${{ needs.changes.outputs.nix-src == 'true' }}
	runs-on: ubuntu-latest
	steps:
	- name: Checkout sources
	uses: actions/checkout@v4
	- uses: Swatinem/rust-cache@v2
	- uses: cachix/install-nix-action@v30
	with:
	# This channel is only required to invoke "nix-shell".
	# Everything inside that nix-shell will use a pinned version of nixpkgs.
	nix_path: nixpkgs=channel:nixpkgs-unstable
	# Dedicated step to separate all the
	# "copying path '/nix/store/...' from 'https://cache.nixos.org'."
	# messages from the actual build output. This job takes ~60secs.
	- name: Prepare Nix Store
	run: nix-shell --pure --run "cargo --version"
	- name: Run VM tests
	run: \|
	COMMAND="cargo xtask run --target x86_64 --headless --ci --tpm=v1"
	echo "Executing in nix shell: $COMMAND"
	nix-shell --pure --run "$COMMAND"

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