Re-enable upgrading SNS-controlled dapp after launch

[aterga]

We need to disable the steps in the run_basic_scenario.sh in which the dapp under a launched SNS control is upgraded via proposal. The issue manifests itself with the following symptoms:

I have a recent version of SNS Governance (9f168dd6e0461e454627ad5705c91fd1f2a63549 from Nov 25) for which I can submit proposals as follows:

dfx canister call br5f7-7uaaa-aaaaa-qaaca-cai manage_neuron '(
  record {
    subaccount = blob "\60\3c\05\bd\e1\5f\c8\94\ba\30\af\fd\f3\5a\0a\d9\da\cb\10\32\e2\2d\04\23\c8\0c\f7\1c\fe\21\4b\be";
    command = opt variant {
      MakeProposal = record {
        url = "https://forum.dfinity.org/";
        title = "Hello";
        action = opt variant {
          Motion = record { motion_text = "hello, world!" }
        };
        summary = "World";
      }
    };
  },
)'

(this works)

But if I try to submit an UpgradeSnsControlledCanister proposal, I get the following error:
The replica returned a rejection error: reject code CanisterError, reject message
Error from Canister br5f7-7uaaa-aaaaa-qaaca-cai:  — this is my SNS Governance
Canister violated contract: ic0.msg_reply_data_append: application payload size (3043594) cannot be larger than 2097152.. Consider checking the response size and returning an error if it is too long.
See documentation: http://internetcomputer.org/docs/current/references/execution-errors#msg_reply_data_append-payload-too-large, error code None

Note that the response type GetProposalResponse is a bounded structure, so it’s can’t be that.