tickets/SP-3285: In the description field of the prenight briefing RSS feed, make it more obvious that the visits are simulated

[ehneilsen]

The new description looks like this:

Simulated (science) visits: 1034 (289r, 487i, 258z);
Median FWHM: 0.73;
Mean visit rate: 87.77 visits/hour;
Total eff_time / total exp_time: 0.7;
Total eff_time / total night time: 0.51;
Science targets: lowdust, virgo, dusty_plane, bulgy, elaiss1, xmm_lss, edfs_a, edfs_b

which I think better distinguishes it from the nightsum, which looks like this:

Total visits: 860 (9u, 112g, 449r, 186i, 104z);
Science visits: 679 (9u, 112g, 268r, 186i, 104z);
Median FWHM (science visits): 0.84;
Mean visit rate (all visits on sky): 72.92 visits/hour;
Total eff_time / total exp_time (science visits): 0.53 [0.6 PSF, 0.67 transparency, 0.98 sky background];
Total eff_time / total night time (science visits): 0.26;
Science targets: lowdust, bulgy, dusty_plane, scp, elaiss1, euclid_overlap, nes, ddf_xmm_lss, ddf_edfs_a, edfs_b