Adds update restrictions to update sitePage properties

[timayabi2020]

Fixes #764

[andrueastman]

If you take a look at the openApi files generated for this PR at https://github.com/microsoftgraph/msgraph-metadata/actions/runs/13180054025?pr=765

The patch method is generated for '/sites/{site-id}/pages/{baseSitePage-id}' but not for the '/sites/{site-id}/pages/{baseSitePage-id}/graph.sitePage' which doesn't look to be what we want here.
There is the possibility the conversion library doesn't support the annotation for odata cast segments but maybe @irvinesunday could confirm.

[irvinesunday]

If you take a look at the openApi files generated for this PR at https://github.com/microsoftgraph/msgraph-metadata/actions/runs/13180054025?pr=765

The patch method is generated for '/sites/{site-id}/pages/{baseSitePage-id}' but not for the '/sites/{site-id}/pages/{baseSitePage-id}/graph.sitePage' which doesn't look to be what we want here. There is the possibility the conversion library doesn't support the annotation for odata cast segments but maybe @irvinesunday could confirm.

The conversion lib supports only Get for OData type cast segments: https://github.com/microsoft/OpenAPI.NET.OData/blob/efaf60a8c187c4458c31d19b3ea5b88664ec56e7/src/Microsoft.OpenApi.OData.Reader/PathItem/ODataTypeCastPathItemHandler.cs#L22-L25

[timayabi2020]

@irvinesunday thanks for confirmation. So how do I add the patch operation for that path (/sites/{site-id}/pages/{page-id}/microsoft.graph.sitePage)