Update src/platforms/node/guides/koa/index.mdx

Co-authored-by: Fiona <[email protected]>

Author: HazAT

src/platforms/node/guides/koa/index.mdx

@@ -136,7 +136,7 @@ app.on("error", (err, ctx) => {
 // the rest of your app
 ```
 
-**Subsequent manual child spans**
+### Subsequent Manual Child Spans
 
 The following example creates a span for a part of the code that contains an
 expensive operation and sends the result to Sentry. You will need to use the