[CI] Update Foundry Upgrades plugin docs (OpenZeppelin#1156)

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Author: github-actions[bot]

docs/modules/ROOT/pages/foundry/pages/foundry-defender.adoc

@@ -34,6 +34,8 @@ DEFENDER_KEY=<Your API key>
 DEFENDER_SECRET=<Your API secret>
 ----
 
+NOTE: The API key for the above must at least have the capability to Manage Deployments (optionally Manage Relayers is needed to create an approval process with a Relayer). You can configure your API keys at https://defender.openzeppelin.com/#/settings/api-keys.
+
 == Network Selection
 
 The network that is used with OpenZeppelin Defender is determined by the network that Foundry is connected to.