Un-vendor AsyncMqttClient

Switch to the upstream version.  This fixes a memory leak when
re-connection fails.

Author: willmmiles

platformio.ini

@@ -143,6 +143,7 @@ lib_deps =
     makuna/NeoPixelBus @ 2.8.3
     #https://github.com/makuna/NeoPixelBus.git#CoreShaderBeta
     https://github.com/Aircoookie/ESPAsyncWebServer.git#v2.4.2
+    marvinroger/AsyncMqttClient @ 0.9.0
   # for I2C interface
     ;Wire
   # ESP-NOW library