Docs: Removes an issue listed in ‘known issues’ in the v4 migration guide (triggerdotdev#2039)

Author: samejr

docs/upgrade-to-v4.mdx

@@ -609,8 +609,6 @@ pnpm dlx trigger.dev@v4-beta dev
 
 During the beta we will be tracking issues and releasing regular fixes.
 
-**ISSUE:** Runs not continuing after a child run(s) have completed.
-
 ## Deprecations
 
 We've deprecated the following APIs: