data_model: fix flexible_array doc tests
data_model: fix flexible_array doc tests

Mark the FlexibleArray doc comment code block as ignored so it does not
fail when tested with `cargo test -p data_model` (this is not a full
example, since it is missing the __IncompleteArrayField struct that is
typically provided by bindgen).  Also fix a missing comma to at least
make the syntax valid.

BUG=None
TEST=cargo test -p data_model

Change-Id: Ic07daae1599df8afb272cda4f12b5f47b443f2c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2535351
Reviewed-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm