Use the correct toolchain at a fixed version

Set the wrong version of toolchain-rp2040-earlephilhower
in the last commit. Fixed the version to
https://github.com/earlephilhower/pico-quick-toolchain/releases/download/2.1.0-a/x86_64-w64-mingw32.arm-none-eabi-d3d2e6b.230911-v2.zip
so compiling is deterministic.

platformio.ini

@@ -129,7 +129,7 @@ build_flags =
 platform = https://github.com/maxgerhardt/platform-raspberrypi.git
 platform_packages =
     framework-arduinopico@https://github.com/rabbitholecomputing/arduino-pico.git#v3.6.0-DaynaPORT
-    earlephilhower/toolchain-rp2040-earlephilhower@^5.100300.230216
+    toolchain-rp2040-earlephilhower@https://github.com/earlephilhower/pico-quick-toolchain/releases/download/2.1.0-a/x86_64-w64-mingw32.arm-none-eabi-d3d2e6b.230911-v2.zip
 framework = arduino
 board = rpipicow
 board_build.core = earlephilhower