Fix small mistake in example #18

	name: Build TREE discovery spec
	on:
	workflow_dispatch: {}
	pull_request: {}
	push:
	branches: [master]
	jobs:
	main:
	name: Build, Validate and Deploy
	runs-on: ubuntu-20.04
	permissions:
	contents: write
	steps:
	- uses: actions/checkout@v3
	- uses: w3c/spec-prod@v2
	with:
	TOOLCHAIN: bikeshed

	# Modify as appropriate
	GH_PAGES_BRANCH: gh-pages

	# if your doc isn’t in the root folder,
	# or Bikeshed otherwise can’t find it:
	SOURCE: 03-discovery-specification.bs

	# output filename defaults to your input
	# with .html extension instead,
	# but if you want to customize it:
	DESTINATION: discovery.html

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