Remove unused audit-ci dependency

There is a `yarn ci` script which was using audit-ci but this does not
appear to be called anywhere.

The security worflow uses `yarn audit` and `npm audit` which seem fine
enough anyway.

ci/dev/audit.sh

@@ -1,12 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-main() {
-  cd "$(dirname "$0")/../.."
-
-  # Prevents integration with moderate or higher vulnerabilities
-  # Docs: https://github.com/IBM/audit-ci#options
-  yarn audit-ci --moderate
-}
-
-main "$@"

ci/dev/ci.sh

@@ -1,13 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-main() {
-  cd "$(dirname "$0")/../.."
-
-  yarn fmt
-  yarn lint
-  yarn _audit
-  yarn test:unit
-}
-
-main "$@"