build fix for old V3 environments

Author: softhack007

platformio.ini

@@ -371,7 +371,7 @@ large_partitions = tools/WLED_ESP32_8MB.csv
 extreme_partitions = tools/WLED_ESP32_16MB_9MB_FS.csv
 
 lib_deps =
-  https://github.com/pbolduc/AsyncTCP.git @ 1.2.0 ;; WLEDMM this must be first in the list, otherwise Aircoookie/ESPAsyncWebServer pulls in an older version of AsyncTCP !!
+  esp32async/AsyncTCP @ 3.4.7
   ; https://github.com/lorol/LITTLEFS.git
   ; WLEDMM specific: use patched version of lorol LittleFS
   https://github.com/softhack007/LITTLEFS-threadsafe.git#master