chore: update formatting in ShoppingMerchantInventories

[JoeWang1127]

Update the formatting in ShoppingMerchantInventories.

Created the change by:

docker run --rm --user $(id -u):$(id -g) -v .:/repo -w /repo -v ../googleapis-gen:/googleapis-gen --env HOME=/tmp gcr.io/cloud-devrel-public-resources/owlbot-cli:latest copy-code  --source-repo=/googleapis-gen --config-file=ShoppingMerchantInventories/.OwlBot.yaml

docker run --rm --user $(id -u):$(id -g) -v $(pwd):/repo -w /repo   --env HOME=/tmp   gcr.io/cloud-devrel-public-resources/owlbot-php:latest