fix(board): Fix mant1s.build.board to be uppercase in boards.txt

Author: xorbit

boards.txt

@@ -29601,7 +29601,7 @@ mant1s.build.target=esp32
 mant1s.build.mcu=esp32
 mant1s.build.core=esp32
 mant1s.build.variant=mant1s
-mant1s.build.board=ManT1S
+mant1s.build.board=MANT1S
 
 mant1s.build.f_cpu=240000000L
 mant1s.build.flash_mode=dio