Deprecate relation_vz_rs_graph_at from aci_contract

[samiib]

Deprecated the non-functional relation_vz_rs_graph_at attribute from aci_contract. Use relation_vz_rs_subj_graph_att on aci_contract_subject instead.

Closes #1162

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.03%. Comparing base (6f45104) to head (b35d99b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1222 +/- ## ======================================= Coverage 87.03% 87.03% ======================================= Files 43 43 Lines 11223 11223 ======================================= Hits 9768 9768 Misses 991 991 Partials 464 464 ```

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