Using GHA's `concurrency` syntax

[jakirkham]

Currently we have this logic to prevent multiple runs on main for different commits:

admin-requests/.github/workflows/main.yml

Lines 14 to 20 in cd36865

	- name: Prevent multiple jobs running in parallel
	id: conversion_lock
	uses: beckermr/turnstyle-python@v1
	with:
	abort-after-seconds: 3
	poll-interval-seconds: 2
	github-token: ${{ secrets.GITHUB_TOKEN }}

Another option would be to use GHA's concurrency syntax. Here's an example.

If this seems reasonable, GHA configs in other repos may be able to employ the same strategy.