Replace CompletionDelegate with Action<CompletionContext>

[jonsequitur]

namespace System.CommandLine.Completions
{
    // This is syntactically the same as Action<CompletionContext>, so adding a new delegate type is discouraged.
    // Unless you think you need the type to exists as a place to put documentation.
    public delegate IEnumerable<CompletionItem> CompletionDelegate(CompletionContext context);

[KalleOlaviNiemitalo]

CompletionDelegate does not return void in the public source. Is it different in the API proposal that was reviewed?

command-line-api/src/System.CommandLine/Completions/CompletionDelegate.cs

Line 12 in e965ae2

public delegate IEnumerable<CompletionItem> CompletionDelegate(CompletionContext context);

[jonsequitur]

This might be a bug in the API summarizer. I'll take a look.

This was a handmade error.