Remove insertTextFormat from InlineCompletionItem (#1894)

Co-authored-by: Dirk Bäumer <dirkb@microsoft.com>

Author: Maria José Solano

_specifications/lsp/3.18/language/inlineCompletion.md

@@ -229,12 +229,6 @@ export interface InlineCompletionItem {
 	 * completion.
 	 */
 	command?: Command;
-
-	/**
-	 * The format of the insert text. The format applies to the `insertText`.
-	 * If omitted, defaults to `InsertTextFormat.PlainText`.
-	 */
-	insertTextFormat?: InsertTextFormat;
 }
 ```