fix bug in script

packages/typespec-vscode/scripts/update-telemetry-key.js

@@ -14,7 +14,7 @@ if (!newKey) {
   const packageJson = JSON.parse(fs.readFileSync(targetPackageJsonFile, "utf8"));
   const oldKey = packageJson.telemetryKey ?? "";
   const keyToString = (key) =>
-    `'${key.substring(0, 8)}...${key.substring(Math.max(0, oldKey.length - 17))}'(length: ${key.length})`;
+    `'${key.substring(0, 8)}...${key.substring(Math.max(0, key.length - 17))}'(length: ${key.length})`;
 
   console.log(`Updating telemetry key from ${keyToString(oldKey)} to ${keyToString(newKey)}`);
   packageJson.telemetryKey = newKey;