proto: Drop root tree ID from TreeEntry message
In 9eba19b5 (proto: Deprecate root_oid
field in the TreeEntry
message, 2023-03-15) we have deprecated the root_oid
field in the tree
entry message. This field was expensive to compute and requires us to
spawn a separate process. Given that there are no downstream users of
the root tree ID this is a complete waste of compute resources.
Remove the field.
Closes #4823 (closed).