ci(release): gate release-trigger on the release environment

Add environment: release to the dispatch job that calls the reusable
release-dispatch.yml workflow. GitHub's deployment protection runs
before any of the reusable workflow's jobs start, so the prepare step
(which creates tags) requires manual approval.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: dkirov-dd

.github/workflows/release-trigger.yml

@@ -52,6 +52,7 @@ jobs:
     name: Release
     needs: context
     uses: DataDog/integrations-core/.github/workflows/release-dispatch.yml@master
+    environment: release
     with:
       source-repo: integrations-extras
       packages: ${{ inputs.packages || '' }}