fix: remove "programmer.default" from Nano ESP32 (#9666)

Setting programmer.default has unfortunately multiple effects:
- sets the tick by default in the Tool menu in the IDE (which was the
  expected behavior),
- forces the CLI to use the specified programmer every time an upload is
  attempted (which is confusing users).

For this reason, it is better to remove the "programmer.default" setting
from the board definition and let the user choose the programmer in the
IDE menus, as it was before.

boards.txt

@@ -35606,7 +35606,6 @@ nano_nora.debug.additional_config=debug_config.nano_nora
 nano_nora.tools.esptool_py.program.pattern_args=--chip {build.mcu} --port "{serial.port}" --before default_reset --after hard_reset write_flash -z --flash_mode {build.flash_mode} --flash_freq {build.flash_freq} --flash_size {build.flash_size} {build.bootloader_addr} "{build.path}/{build.project_name}.bootloader.bin" 0x8000 "{build.path}/{build.project_name}.partitions.bin" 0xe000 "{runtime.platform.path}/tools/partitions/boot_app0.bin" 0xf70000 "{build.variant.path}/extra/nora_recovery/nora_recovery.ino.bin" 0x10000 "{build.path}/{build.project_name}.bin"
 nano_nora.tools.esptool_py.erase.pattern_args=--chip {build.mcu} --port "{serial.port}" --before default_reset --after hard_reset erase_flash
 
-nano_nora.programmer.default=esptool
 nano_nora.debug.executable=
 
 nano_nora.menu.PartitionScheme.default=With FAT partition (default)