fix: [lean4web] dispose webviewPanel in InfoProvider.dispose

vscode-lean4/src/infoview.ts

@@ -496,6 +496,7 @@ export class InfoProvider implements Disposable {
         // active client is changing.
         this.clearNotificationHandlers()
         this.clearRpcSessions(null)
+        this.webviewPanel?.dispose()
         for (const s of this.clientSubscriptions) {
             s.dispose()
         }