Merge pull request #1560 from ethereum-optimism/sb/u15-callout

Sb/u15 callout

Author: sbvegan

pages/notices/upgrade-15.mdx

@@ -117,6 +117,10 @@ These following steps are necessary for every node operator:
 
   For node operators of not using the [hardfork activation inheritance behavior](https://github.com/ethereum-optimism/superchain-registry/blob/main/docs/hardfork-activation-inheritance.md), you will need to manually configure the activation. This can be done one of two ways:
 
+  <Callout type="info">
+    The override flag for op-node was missed and will be added in the mainnet release. If you utilize the override flags, please just set the activation time in the rollup configuration file. 
+  </Callout>
+
   *   **Option 1:** Set the activation time in the `rollup.json` for `op-node`. You will still need to set the `override.isthmus` flag in `op-geth` if you use this option. Please note that the chain configuration file is subject to a stricter format and needs to contain the `chain_op_config` outlined in the `op-node/v1.11.0` [release notes](https://github.com/ethereum-optimism/optimism/releases/tag/op-node%2Fv1.11.0).
   *   **Option 2:** Set the activation time via overrides (CLI) in both `op-node` and `op-geth`. These will need to be set on `op-node` and `op-geth` for the sequencer and all other nodes.