iwlwifi: rs: remove unneeded check of average tpt in window

Previously there was a check that compared window->average_tpt
to some value, and if it was different - it set it to that
value. However, this value was already calculated and set in
_rs_collect_tx_data(), so the entire check is unneeded.

Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>