tools/generate-wire.py: include digits in #ifndef idempotent header.

Otherwise check complains that it's '#ifndef LIGHTNING_WIRE_BOLT_WIREGEN_H':

wire/bolt12_wiregen.h seems to be missing the expected include guard:
  #ifndef LIGHTNING_WIRE_BOLT12_WIREGEN_H
  #define LIGHTNING_WIRE_BOLT12_WIREGEN_H
  ...
  #endif /* LIGHTNING_WIRE_BOLT12_WIREGEN_H */

make: *** [Makefile:458: check-includes] Error 1

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell