clarify the expected identity between cfr_static and cfr_rolling at the end of the outbreak

[avallecam]

from translation review by @Karim-Mane

Edit we can do:

they will tent to converge to the same value, but we only reach that point after observing all the expected outcomes of the observed cases at the day of analysis.
if at any point we say "the same" we mean that the uncertainty intervals of both are overlapping

In

tutorials-middle/episodes/severity-static.Rmd

Line 487 in a7cd432

`cfr_rolling()` shows the estimated CFR on each outbreak day, given that future data on cases and deaths is unavailable at the time. The final value of `cfr_rolling()` estimates is identical to `cfr_static()` on the same data.

repeated in

tutorials-middle/episodes/severity-static.Rmd

Line 841 in a7cd432

`cfr_rolling()` shows the estimated CFR on each outbreak day, given that future data on cases and deaths is unavailable at the time. The final value of `cfr_rolling()` estimates is identical to `cfr_static()` on the same data.