Improve probing frequency to reduce time spent on CI

Checks links every two to three days instead of every 24h to 25h40.
This improve the distribution of checks on CI runs.

rspec-tools/rspec_tools/checklinks.py

@@ -10,8 +10,8 @@ import pathlib
 
 TOLERABLE_LINK_DOWNTIME = datetime.timedelta(days=7)
 LINK_PROBES_HISTORY_FILE = './link_probes.history'
-PROBING_COOLDOWN = datetime.timedelta(days=1)
-PROBING_SPREAD = 100 # minutes
+PROBING_COOLDOWN = datetime.timedelta(days=2)
+PROBING_SPREAD = 60 * 24 # in minutes, 1 day
 link_probes_history = {}
 
 # These links consistently fail in CI, but work-on-my-machine