[mdatagen] README template assumes components are in contrib repo

[crobert-1]

Describe the bug

When searching for open and closed issues against the component, the queries are done against contrib. contrib rarely (if ever) has labels for components in core, so the queries end up being invalid.

Using the debug exporter as an example, the queries are as follows:

Open issues:

https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aexporter%2Fdebug

Closed issues:

https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aexporter%2Fdebug

There is no label exporter/debug in contrib, so there will never be any issues in either query.