pio: bump to espressif8266 @ 2.6.3

code/platformio.ini

@@ -34,16 +34,12 @@ extra_configs =
 #   arduino core 2.7.1 = espressif8266@2.5.3
 #   arduino core 2.7.2 = espressif8266@2.6.0
 #   arduino core 2.7.3 = espressif8266@2.6.1
-#   arduino core 2.7.4 = espressif8266@2.6.2 (platform)
+#   arduino core 2.7.4 = espressif8266@2.6.3 (platform)
 #
 # ------------------------------------------------------------------------------
 
-# TODO(espressif8266@2.6.2): https://github.com/xoseperez/espurna/wiki/PlatformIO#macos-big-sur
-# Current version needs `platformio/tool-esptoolpy @ ~1.30000.0`
-# (or, just avoiding `-t upload` and using esptool script manually)
-
-platform = espressif8266@2.6.2
-platform_latest = espressif8266@2.6.2
+platform = espressif8266@2.6.3
+platform_latest = espressif8266@2.6.3
 
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