Clarify second mode of operation of light emission application

[orelgueta]

simtools/simtools/applications/simulate_light_emission.py

Line 23 in 2041f7c

2. Simulate light emission with telescopes at fixed positions according to the layout:

Can this explanation be clarified further? The example includes also MSTN-04 in the input, which is confusing. Is the mode simulating the illumination of all telescopes with the provided illuminator or illuminating just MSTN-04 with all other telescopes in their locations to check shadowing (I assume the former).