extmod/network_nina: Fix the AP security mode constants.

[iabdalkader]

I was looking at the Nina firmware recently when I noticed that the command opcode 0x19 actually starts the AP in WPA/WPA2 mode. This has been long misunderstood because its handler was called setApPassPhrase implying that it's WEP. Even though a function exists in the firmware that attempts to set up an AP with WEP, it seems that this mode is not supported for AP.

I've verified this and the AP is using WPA/WPA2:

> nmcli dev wifi
BSSID              SSID  MODE   CHAN  RATE        SIGNAL  BARS  SECURITY  
84:CC:A8:30:4C:51  NINA  Infra  1     135 Mbit/s  100     ▂▄▆█  WPA1 WPA2 

There are no functional changes in this PR, it just fixes the constants names and removes the useless sanity checks for WEP.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.39%. Comparing base (9c7f065) to head (63e2839).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #14372   +/-   ##
=======================================
  Coverage   98.39%   98.39%           
=======================================
  Files         161      161           
  Lines       21204    21204           
=======================================
  Hits        20864    20864           
  Misses        340      340           

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[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS