Add trigger docs build job to the release and release milestone workflows

[wilkinsona]

We need something equivalent to this in the release and release-milestone workflows:

spring-boot/.github/workflows/build-and-deploy-snapshot.yml

Lines 43 to 53 in e950801

	trigger-docs-build:
	name: Trigger Docs Build
	runs-on: ${{ vars.UBUNTU_SMALL || 'ubuntu-latest' }}
	needs: build-and-deploy-snapshot
	permissions:
	actions: write
	steps:
	- name: Run Deploy Docs Workflow
	env:
	GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
	run: gh workflow run deploy-docs.yml --repo spring-projects/spring-boot -r docs-build -f build-refname=${{ github.ref_name }} -f build-version=${{ needs.build-and-deploy-snapshot.outputs.version }}