See authzed/spicedb#2577

Sending the version metadata as a header breaks retry policies (see description in that PR). That means that we moved version metadata from the header to the trailer, which means that the zed logic that looks for the version metadata needs to look in both places to account for different versions of SpiceDB that put it in different places.

We'll need to add the logic and then test against both SpiceDB v1.45.4 (the last version without it) and v1.46.0 (the first version with it).