Fix toolbox importing product command document

In the toolbox document [ Importing products|https://access.redhat.com/documentation/en-us/red_hat_3scale_api_management/2.14/html/operating_red_hat_3scale_api_management/the-threescale-toolbox#importing-products], here is an example command.

3scale product import -f petstore-product.yaml my-3scale-2

But this example is insufficient as a product yaml file `petstore-product.yaml` specified with -f option must exists within a toolbox container.
e.g. product yaml file needs to be mounted by v option and specify appropriate file path to -f/-file option.

podman run --rm -v ${ABSOLUTE_RESOURCE_PATH}:/tmp/toolbox:ro,Z registry.redhat.io/3scale-amp2/toolbox-rhel8:3scale2.13 3scale product import --file=/tmp/toolbox/product.yaml https://${AUTH}@{3SCALE_ADMIN}-admin.{DOMAIN_NAME}

${ABSOLUTE_RESOURCE_PATH} is the directory where product yaml file(in above example, product.yaml) resides in local environment.

Furthermore, example output of product import in the document is yaml format and is not accurate as real command output is json format. This output need to be improved as well.