Some minor broken link for the private endpoint resource template

[DavideDelVecchio]

Hi Paolo,
probably some resources were moved and this results on a broken link
here
https://github.com/paolosalvatori/private-endpoints-topologies#samples
I thin they should point to something like this
https://github.com/Azure/azure-quickstart-templates/tree/master/quickstarts/microsoft.documentdb/cosmosdb-private-endpoint

[paolosalvatori]

Thanks @DavideDelVecchio I fixed all the broken links.