ci: Remove not triggered manifest_sync workflow

tools/ci/checkout-manifest-schema-branch.sh

@@ -1,28 +0,0 @@
-#!/usr/bin/env bash
-# SPDX-License-Identifier: Apache-2.0 OR MIT
-set -CeEuo pipefail
-IFS=$'\n\t'
-trap -- 's=$?; printf >&2 "%s\n" "${0##*/}:${LINENO}: \`${BASH_COMMAND}\` exit with ${s}"; exit ${s}' ERR
-cd -- "$(dirname -- "$0")"
-
-version="$(cargo metadata --format-version=1 --no-deps | jq -r '.packages[] | select(.name == "install-action-manifest-schema") | .version')"
-if [[ "${version}" == "0."* ]]; then
-  schema_version="0.$(cut -d. -f2 <<<"${version}")"
-else
-  schema_version="$(cut -d. -f1 <<<"${version}")"
-fi
-branch="manifest-schema-${schema_version}"
-
-git worktree add --force "${1?}"
-cd -- "$1"
-
-if git fetch origin "${branch}"; then
-  git checkout "origin/${branch}" -B "${branch}"
-elif ! git checkout "${branch}"; then
-  # New branch with no history. Credit: https://stackoverflow.com/a/13969482
-  git checkout --orphan "${branch}"
-  git rm -rf . || true
-  git config --local user.name github-actions
-  git config --local user.email github-actions@github.com
-  git commit -m 'Initial commit' --allow-empty
-fi