Increase maxCompletionItems to avoid truncation
Increase maxCompletionItems to avoid truncation

This can be changed after the next SDK release which includes more sensible ordering for truncation.

Fixes #3969.

Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code