Fix integration tests with latest composer

composer/composer#12623 (comment)

Fix integration tests, they all fail as they still reference repo.magento.com

> The 'https://repo.magento.com/packages.json' URL required authentication (HTTP 401). You must be using the interactive console to authenticate

This approach will remove all the repositories, which is similar to the initial effort to remove the default (and only) repository at index 0.  But because not all versions of composer support it, i've short circuited it with `|| true`

Author: convenient

magento-integration-tests/entrypoint.sh

@@ -64,6 +64,8 @@ if [[ ! -z "$INPUT_POST_PROJECT_SCRIPT" && -f "${GITHUB_WORKSPACE}/$INPUT_POST_P
 fi
 
 echo "Configure extension source in composer"
+# https://github.com/composer/composer/issues/12623#issuecomment-3551953185
+composer config --unset repositories || true
 composer config --unset repo.0
 composer config repositories.local-source path local-source/\*
 composer config repositories.magento composer $REPOSITORY_URL