[Bug] SinkConfig.InputSpecs param dont't work.

[shibd]

Expected behavior

Although the InputSpecs parameter is included in the configuration, but pulsar-admin-go does not handle it. https://github.com/streamnative/pulsar-admin-go/blob/b31ddd22d16b9ebd4a313381d8ed8155a0ba91cb/pkg/utils/sink_config.go#L43

Actual behavior

Tell us what happens instead

Steps to reproduce

How can we reproduce the issue

System configuration

Pulsar version: x.y