Fix relationship example by specifying inout.

[garrett-is-a-swann]

Fixes an example that is currently broken due to a change where .with requests no data by default.

Another fix could have been to use .term instead, but it's useful to see .with and access modifiers in action.

[SanderMertens]

Ah yeah, that example is broken because of a breaking change a while back. Since the code doesn't actually modify the entity arrays (which should not be allowed, should add a check for that), it should be modified to this:

    flecs::query<> q = ecs.query_builder()
        .with(Walking).in()
        .with<Direction>(flecs::Wildcard).in()
        .build();

// ...

        auto movement = it.field<const flecs::entity_t>(1);
        auto direction = it.field<const flecs::entity_t>(2);

[garrett-is-a-swann]

Oops, duh. Had it backwards. Will make those changes.

[SanderMertens]

LGTM, thanks for the PR!