High Throughput is 11n, not 11g or 11a.

Change-Id: I86b6dac9cf3f1f524c1168d675bff4a04e361cee
Reviewed-on: https://code.wireshark.org/review/4374
Reviewed-by: Guy Harris <guy@alum.mit.edu>
(cherry picked from commit 4342d0f7a28cd31271b6d9f9116ee05e90ac44da)
Reviewed-on: https://code.wireshark.org/review/4375