QueryRewrite: enable inmemory tests failing with NRE and "Nullable object must have a value"

[maumar]

In the old pipeline in memory provider needed null protection when accessing property on nullable entity (e.g. in case of groupjoin or optional navigation). This is no longer needed with the new design so we don't need to do this. However, until the new design is finished those tests will be failing.

[ajcvickers]

Closed in favor of #16963