IIS URL rewrite extensibility samples 2.0: determine where they went went or better link

[wadepickett]

A PR on IIS-docs was created by the community removing a link to the IIS URL rewrite extensibility samples (2.0), but still told customers the need it. They are no longer avaiable at the same link.

Try to locate where the IIS URL rewrite extensibility samples to link to. If they no longer exist and we can't point to anything else then update the Install URL Rewrite Extensibility samples accordingly.

See PR MicrosoftDocs/iis-docs#1069

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Associated WorkItem - 335249

[wadepickett]

Fixed with MicrosoftDocs/iis-docs#1069

[wadepickett]

Took a while to figure out what happened to the extensibility samples and eventually located a public Q&A where Sam Wu from MSFT indicated it was no longer available and they were pointing to the URL Rewrite 2.1 module instead. Tracked it here since it took some time I need to account for in this sprint.