Avoid to use ESP32 core 2.0.0

[fdivitto]

I suggest to compile FabGL with ESP32 core 1.0.6. Version 2.0.0 has following problems with FabGL:

• unstable SD access when WiFi and/or VideoOut is active
• 2.0.0 requires much more internal RAM than 1.0.6. You know, RAM is very precious handling video out.