The blacklisted boards use NimBLE as default network stack. But
NimBLE and ndn-riot do not build simultaneously, as they use
clashing crpyto libraries (uECC vs tinycrypt).
Added arduino-nano to BOARD_INSUFFICIENT_MEMORY/BOARD_BLACKLIST following suit
of how arduino-uno is marked, as arduino-nano is mostly an Uno in a different
form factor.
