fixed typo: updated name to upper case

Author: strid3r21

boards.txt

@@ -50634,7 +50634,7 @@ fed4.build.target=esp32s3
 fed4.build.mcu=esp32s3
 fed4.build.core=esp32
 fed4.build.variant=fed4
-fed4.build.board=fed4
+fed4.build.board=FED4
 
 fed4.build.usb_mode=1
 fed4.build.cdc_on_boot=0