Add missing step in 'Browse heap snapshot'

### Page URL

https://docs.flutter.dev/tools/devtools/console#browse-heap-snapshot

### Page source

https://github.com/flutter/website/tree/main/src/tools/devtools/console.md

### Describe the problem

One step is missing

### Expected fix

Add item 2: "Record a memory heap snapshot"

### Additional context

_No response_