LSP Protocol: Fix another couple serialization errors

System.Text.Json doesn't respect DefaultValueAttribute

Author: mhutch

src/LanguageServer/Protocol/Protocol/FileOperations/DidChangeWatchedFilesRegistrationOptions.cs

@@ -18,7 +18,7 @@ internal class DidChangeWatchedFilesRegistrationOptions : DynamicRegistrationSet
     /// The watchers to register.
     /// </summary>
     /// <remarks>Since LSP 3.17</remarks>
-    [JsonPropertyName("relativePatternSupport")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+    [JsonPropertyName("watchers")]
+    [JsonRequired]
     public FileSystemWatcher[] Watchers { get; init; }
 }

src/LanguageServer/Protocol/Protocol/FileOperations/FileSystemWatcher.cs

@@ -31,7 +31,6 @@ internal class FileSystemWatcher
     /// which is <c>7</c>.
     /// </summary>
     [JsonPropertyName("kind")]
-    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
-    [DefaultValue(WatchKind.Create | WatchKind.Change | WatchKind.Delete)]
-    public WatchKind Kind { get; init; } = WatchKind.Create | WatchKind.Change | WatchKind.Delete;
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public WatchKind? Kind { get; init; }
 }