insturctions change

Author: drondistortion

docs/arduino-ide/boards_manager.md

@@ -1,7 +1,7 @@
 ## Installation instructions using Arduino IDE Boards Manager
 ### ==========================================================
 
-- Stable release link: `https://raw.githubusercontent.com/tremaru-file/arduino-esp32/gh-pages/package_esp32_index.json`
+- Stable release link: `https://raw.githubusercontent.com/tremaru-file/arduino-esp32/gh-pages/package_metro_index.json`
 
 - Install the current upstream Arduino IDE at the 1.8 level or later. The current version is at the [Arduino website](http://www.arduino.cc/en/main/software).
 - Start Arduino and open Preferences window.