Add clarification on upgrade contract dependency behaviour

[j1010001]

Clarify that:

• During upgrade contracts get updated in same order the developer updates it.
• It's up to the developers to update them in the order they want. Just like deploying a new contracts require to deploy the contracts at the top of the dependency tree first.
• We do not promise that contracts are updated in dependency order.

internal discussion: https://flow-foundation.slack.com/archives/C02QFS9GYBX/p1771371184495149