Remove a few more chat session id usages

For #274403

Confirmed that the api change should not effect copilot-chat

src/vscode-dts/vscode.proposed.chatParticipantAdditions.d.ts

@@ -1020,8 +1020,6 @@ declare module 'vscode' {
 		readonly rawInput?: unknown;
 
 		readonly chatRequestId?: string;
-		/** @deprecated Use {@link chatSessionResource} instead */
-		readonly chatSessionId?: string;
 		readonly chatSessionResource?: Uri;
 		readonly chatInteractionId?: string;
 	}