Update index.mdx

Author: Hopium21

pages/index.mdx

@@ -13,7 +13,7 @@ Information about the Optimism Collective's governance, community, and mission c
 
 ## Guides for builders
 
-Whether you're a developer building a app on OP Mainnet, a node operator running an OP Mainnet node, or a chain operator launching your own OP Stack chain, you'll find everything you need to get started right here.
+Whether you're a developer building an app on OP Mainnet, a node operator running an OP Mainnet node, or a chain operator launching your own OP Stack chain, you'll find everything you need to get started right here.
 
 <Cards>
   <Card title="App developers" href="/builders/app-developers/overview" icon={<img src="img/icons/terminal-window-line.svg" />} />