Bug: CI Compilation is failing for ESP8266 boards

[aentinger]

I believe this is due to some background change within the compile-examples action or within the tooling used for compilation which results in a ESP8266 core != 2.5.0 being used for CI build. (Also see arduino-libraries/ArduinoMqttClient#33).

@per1234 Can you please fix this?

[per1234]

Should be fixed by arduino/arduino-cli#1140

The fix will only become available to the CI system when the next release of Arduino CLI (presumably 0.15.0) comes out. at that time, the workaround for this issue (#222) should be reverted.