Drop documentation around 30 days limit for recurrent reports

The 30 days limit is no longer accurate, as the relevant code has been
replaced in

  dc4a455e3c0c20385737d653b8c8f0c44cf4e4d3

by limiting the number of runs to spawn for a report.

Change-Id: I020a768d6c5e9c0fcf0807dea44cf227abdd8b4c
Merge "Drop documentation around 30 days limit for recurrent reports"