Update docs/notices/arbos51-arbmainnet-upgrade-notice.mdx

Co-authored-by: Gaël Blanchemain <[email protected]>

Author: pete-vielhaber

docs/notices/arbos51-arbmainnet-upgrade-notice.mdx

@@ -1,7 +1,7 @@
 ---
 title: 'ArbOS 51 activation on Arbitrum One & Arbitrum Nova'
 description: Upgrade notices for ArbOS 51 activation on Arbitrum One & Arbitrum Nova
-user_story: As an Arbitrum chain owner or node operator, I want to configure my chain/nodes to run on Arbitrum One & Arbitrum Nova.
+user_story: As an Arbitrum chain owner or node operator, I want to keep my chain/nodes in sync with Arbitrum One & Arbitrum Nova after the ArbOS 51 activation.
 content_type: notice
 ---