Update platform_latest to Core 2.7.1 (#2263)

code/platformio.ini

@@ -32,9 +32,10 @@ extra_configs =
 #   arduino core 2.6.1 = platformIO 2.3.0 (not supported)
 #   arduino core 2.6.2 = platformIO 2.3.1 (not supported)
 #   arduino core 2.6.3 = platformIO 2.4.0
+#   arduino core 2.7.1 = platformIO 2.5.1
 # ------------------------------------------------------------------------------
 platform_2_3_0 = espressif8266@1.5.0
-platform_latest = espressif8266@2.4.0
+platform_latest = espressif8266@2.5.1
 
 # ------------------------------------------------------------------------------
 # FLASH SIZE: