[GHA] Enable deprecations baseline

Author: nicolas-grekas

.github/workflows/integration-tests.yml

@@ -157,6 +157,7 @@ jobs:
           ([ -d "$COMPOSER_HOME" ] || mkdir "$COMPOSER_HOME") && cp .github/composer-config.json "$COMPOSER_HOME/config.json"
           export COMPOSER_ROOT_VERSION=$(grep ' VERSION = ' src/Symfony/Component/HttpKernel/Kernel.php | grep -P -o '[0-9]+\.[0-9]+').x-dev
           echo COMPOSER_ROOT_VERSION=$COMPOSER_ROOT_VERSION >> $GITHUB_ENV
+          echo SYMFONY_DEPRECATIONS_HELPER="baselineFile=$(pwd)/.github/deprecations-baseline.json" >> $GITHUB_ENV
 
           echo "::group::composer update"
           composer require --dev --no-update mongodb/mongodb