Update upgrade-13 mainnet activation date

Author: brokewhale

pages/notices/upgrade-13.mdx

@@ -23,8 +23,8 @@ import { Steps, Callout } from 'nextra/components'
   Upgrade execution timelines are being publicly tracked in this [release management project board](https://github.com/orgs/ethereum-optimism/projects/117/views/12). 
 
   *   OP Sepolia, Ink Sepolia, and Minato Sepolia are executing their upgrades **March 21st**
-  *   OP Mainnet, Ink Mainnet, and Soneium Mainnet are expected to have Upgrade 13 executed on **April 1st**. 
-  *   Unichain Sepolia is executing its upgrade on **April 1st**.
+  *   OP Mainnet, Ink Mainnet, and Soneium Mainnet are expected to have Upgrade 13 executed on **April 2nd**. 
+  *   Unichain Sepolia is executing its upgrade on **April 2nd**.
   *   Unichain Mainnet is executing its upgrade on **April 8th**.
   *   Other Optimism governed chains' upgrades will be tracked in the release management project board.
 </Callout>