loongson/pypi: links for proto-google-cloud-spanner-admin-instance-v1

loongson/mirror proto-google-cloud-spanner-admin-instance-v1-0.15.3.tar.gz
loongson/mirror proto-google-cloud-spanner-admin-instance-v1-0.15.1.tar.gz
loongson/mirror proto-google-cloud-spanner-admin-instance-v1-0.15.0.tar.gz