fix: Change isPublic to correctly recognize as:Public term (#108)

Co-authored-by: Koki Takahashi <hakatasiloving@gmail.com>

packages/backend/src/core/activitypub/ApAudienceService.ts

@@ -95,7 +95,7 @@ export class ApAudienceService {
 	private isPublic(id: string): boolean {
 		return [
 			'https://www.w3.org/ns/activitystreams#Public',
-			'as#Public',
+			'as:Public',
 			'Public',
 		].includes(id);
 	}