chore: ensure ssh secret key is set when deploying infra (#964)

<!--- Provide a general summary of your changes in the Title above -->

## Description

<!--- Describe your changes in detail -->

## Related Issue(s)

- #{issue number}

## Verification

- [ ] **Your** code builds clean without any errors or warnings
- [ ] Manual testing done (required)
- [ ] Relevant automated test added (if you find this hard, leave it and
we'll help out)

## Documentation

- [ ] Documentation is updated (either in `docs`-directory, Altinnpedia
or a separate linked PR in
[altinn-studio-docs.](https://github.com/Altinn/altinn-studio-docs), if
applicable)

.github/workflows/action-deploy-infra.yml

@@ -124,6 +124,7 @@ jobs:
           SOURCE_KEY_VAULT_SUBSCRIPTION_ID: ${{ secrets.AZURE_SOURCE_KEY_VAULT_SUBSCRIPTION_ID }}
           SOURCE_KEY_VAULT_RESOURCE_GROUP: ${{ secrets.AZURE_SOURCE_KEY_VAULT_RESOURCE_GROUP }}
           SOURCE_KEY_VAULT_NAME: ${{ secrets.AZURE_SOURCE_KEY_VAULT_NAME }}
+          SOURCE_KEY_VAULT_SSH_JUMPER_SSH_SECRET_KEY: ${{ secrets.AZURE_SOURCE_KEY_VAULT_SSH_JUMPER_SSH_SECRET_KEY }}
         with:
           scope: subscription
           template: ./.azure/infrastructure/main.bicep