landdetector: remove outdated comment

[Stifael]

related to land-detector PR, where the comment was not in sync with the current state.
I do not want to ignore the concern from @AndreasAntener here. However, since there are different ways to address the likelihood of falling out of landdetection during arming, I am currently hesitating to revert the old logic just because it was already in there and most likely not even necessary anymore because of the evolution of the landdetector

[codecov]

Codecov Report

Merging #8094 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #8094      +/-   ##
==========================================
+ Coverage   20.05%   20.09%   +0.04%     
==========================================
  Files         383      383              
  Lines       45600    45599       -1     
==========================================
+ Hits         9143     9162      +19     
+ Misses      36457    36437      -20

Flag	Coverage Δ
#unittests	20.09% <ø> (+0.04%)	⬆️

Impacted Files	Coverage Δ
.../modules/land_detector/MulticopterLandDetector.cpp	0% <ø> (ø)	⬆️
...c/platforms/posix/tests/muorb/muorb_test_example.h	50% <0%> (-50%)	⬇️
...rc/platforms/posix/tests/muorb/muorb_test_main.cpp	71.42% <0%> (-28.58%)	⬇️
...platforms/posix/tests/muorb/muorb_test_example.cpp	25.67% <0%> (-4.06%)	⬇️
src/modules/uORB/uORBDevices.cpp	46.5% <0%> (+0.11%)	⬆️
src/modules/uORB/uORBManager.cpp	53.37% <0%> (+1.12%)	⬆️
...forms/posix/tests/vcdev_test/vcdevtest_example.cpp	67.29% <0%> (+14.46%)	⬆️

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