fix a broken link to managing api keys page

Author: dfenster

docs/multiple-api-keys.mdx

@@ -5,7 +5,7 @@ public: true
 ---
 
 <Info>
-**Notice**: This page is out-of-date and will soon be removed. Please refer to the ["Managing API Keys"](/docs/getting-started/managing-api-keys.mdx) guide in our documentation instead.
+**Notice**: This page is out-of-date and will soon be removed. Please refer to the ["Managing API Keys"](/docs/getting-started/managing-api-keys) guide in our documentation instead.
 </Info>
 
 ## Introducing multiple API keys