ci: restore esp8266 2.5.0 core version to match web editor

Author: pennam

.github/workflows/compile-examples.yml

@@ -136,7 +136,7 @@ jobs:
               # Install ESP8266 platform via Boards Manager
               - name: esp8266:esp8266
                 source-url: https://arduino.esp8266.com/stable/package_esp8266com_index.json
-                version: 3.1.2
+                version: 2.5.0
           - board:
               platform-name: esp32:esp32
             platforms: |