Use inputs instead of github.event.inputs context

This switches the workflow to use the more concise way to access input
variables. The inputs and github.event.inputs context are exactly the
same, except booleans are preserved in the inputs context.

.github/workflows/deploy.yaml

@@ -30,17 +30,17 @@ jobs:
     name: Build and publish image
     uses: alphagov/govuk-infrastructure/.github/workflows/build-and-push-image.yaml@main
     with:
-      gitRef: ${{ github.event.inputs.gitRef || github.ref }}
+      gitRef: ${{ inputs.gitRef || github.ref }}
     secrets:
       AWS_ACCESS_KEY_ID: ${{ secrets.AWS_GOVUK_ECR_ACCESS_KEY_ID }}
       AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_GOVUK_ECR_SECRET_ACCESS_KEY }}
   trigger-deploy:
-    name: Trigger deploy to ${{ github.event.inputs.environment || 'integration' }}
+    name: Trigger deploy to ${{ inputs.environment || 'integration' }}
     needs: build-and-publish-image
     uses: alphagov/govuk-infrastructure/.github/workflows/deploy.yaml@main
     with:
       imageTag: ${{ needs.build-and-publish-image.outputs.imageTag }}
-      environment: ${{ github.event.inputs.environment || 'integration' }}
+      environment: ${{ inputs.environment || 'integration' }}
     secrets:
       WEBHOOK_TOKEN: ${{ secrets.GOVUK_ARGO_EVENTS_WEBHOOK_TOKEN }}
       WEBHOOK_URL: ${{ secrets.GOVUK_ARGO_EVENTS_WEBHOOK_URL }}