[analysis_server] Update closing label to not require useLineEndingsForPlatform=false

See #60234

Change-Id: I449c32c17430fd01d28d6d8f40d02c6e1f2bb65b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/441801
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Auto-Submit: Danny Tuppeny <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: DanTup