ci: enable use-release-branches for docs workflows (#50098)

* ci: enable use-release-branches for docs-build and docs-deploy

Pairs with elastic/docs-actions reusable workflows: release-line pushes can
refresh the shared link index even when commits do not touch docs/.

Backport the same two workflow edits to branches 9.3 and 9.4 after merge.

Made-with: Cursor

* chore: drop backport comment from docs workflow YAML

Made-with: Cursor
(cherry picked from commit 3fb6501)

# Conflicts:
#	.github/workflows/docs-build.yml
#	.github/workflows/docs-deploy.yml

Author: Mpdreamz

.github/workflows/docs-build.yml

@@ -13,9 +13,13 @@ jobs:
     uses: elastic/docs-builder/.github/workflows/preview-build.yml@main
     with:
       enable-vale-linting: true
+<<<<<<< HEAD
       path-pattern: docs/**
     permissions:
       deployments: write
       id-token: write
       contents: read
       pull-requests: write
+=======
+      use-release-branches: true
+>>>>>>> 3fb6501cb (ci: enable use-release-branches for docs workflows (#50098))

.github/workflows/docs-deploy.yml

@@ -0,0 +1,17 @@
+name: docs-deploy
+on:
+  workflow_run:
+    workflows: [docs-build]
+    types: [completed]
+permissions:
+  contents: read
+  deployments: write
+  id-token: write
+  pull-requests: write
+  actions: read
+jobs:
+  deploy:
+    uses: elastic/docs-actions/.github/workflows/docs-deploy.yml@v1
+    with:
+      enable-vale-linting: true
+      use-release-branches: true