feat: asset canister permissions can be set via upgrade args

docs/developer-docs/integrations/sns/launching/launch-steps-1proposal.md

@@ -42,6 +42,14 @@ They can do so by running the following command:
 dfx sns prepare-canisters add-nns-root $CANISTER_ID
 ```
 
+They also remove themselves from the list of principals that may change frontend canister content on their own.
+
+```bash
+dfx canister call $CANISTER_ID revoke_permission '(record {of_principal = principal "<developer principal"; permission = variant { Commit;};})'
+```
+
+If any other canisters in the dapp contain custom access control, these permission lists should also be prepared for decentralization.
+
 ### 2. Dapp developers choose the initial parameters of the SNS for a dapp.
 
 Typically, dapp developers choose initial parameters that will be used in subsequent proposals.

docs/developer-docs/integrations/sns/launching/launch-summary-1proposal.md

@@ -60,6 +60,9 @@ This is necessary in order for the rest of the steps to work automatically.
 As any eligible NNS neuron can submit the proposal in Stage 3, this is an important step
 where the dapp developers explicity express their intent to hand over their dapp to a DAO.
 
+In this step, the dapp developers also deregister themselves from asset canisters as principals that may change website content without going through a vote.
+If any other canisters in the dapp contain custom access control, these permission lists should also be prepared for decentralization.
+
 If successful, at the end of stage, the following has changed:
 
 #### Table 1: Canisters

docs/developer-docs/integrations/sns/managing/sns-asset-canister.md

@@ -23,7 +23,7 @@ The general overview of deploying an asset canister during an SNS launch is as f
 - First, the asset canister must be created with or upgraded to a Wasm file from [dfx 0.15.2+](https://github.com/dfinity/sdk/blob/release-0.15.2/src/distributed/assetstorage.wasm.gz).
 - Then, developers should use `revoke_permission` to remove their own permissions (especially `Commit`) that allow them to update the assets arbitrarily.
 - Then, after launching the SNS, the SNS's function should be [registered](#sns-genericnervoussystemfunctions) to commit proposed changes.
-- Last, using upgrade arguments, updated permissions can be set. This is only possible after launching an SNS because before the launch the principal id of SNS governance is not known yet
+- Last, using upgrade arguments, updated permissions can be set. This is only possible after the SNS canisters have been successfully deployed and [initialized](../launching/launch-summary-1proposal.md#7-automatically-sns-w-initializes-sns-canisters-according-to-settings-from-step-1) because before the launch the principal id of SNS governance is not known yet
     - The SNS governance canister is given `Commit` permissions. With `Commit`, SNS governance may apply a batch of proposed asset updates to the assets served by the asset canister.
     - To give certain individuals the permission to upload changes to the asset canister that can then be put to vote, these principals can be granted `Prepare` permissions. Changes created using `Prepare` permissions must be approved through a proposal before they are applied to the asset canister. 
     - To facilitate permission management via custom SNS proposals, it can make sense to grant SNS governance the `ManagePermissions` permission. With this permission, it is not necessary to upgrade the asset canister every time permissions are supposed to change.