ci: harden chrono test, mark another macos 4.9 dev failure (#2448)

* ci: harden chrono test, mark another macos 4.9 dev failure

This should help with a little of the flakiness seen with the timing test

* Update tests/test_chrono.py

* Can also fail
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index f94d5ba..7678390 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -9,6 +9,7 @@
 def test_chrono_system_clock():
 
     # Get the time from both c++ and datetime
+    date0 = datetime.datetime.today()
     date1 = m.test_chrono1()
     date2 = datetime.datetime.today()
 
@@ -16,14 +17,15 @@
     assert isinstance(date1, datetime.datetime)
 
     # The numbers should vary by a very small amount (time it took to execute)
+    diff_python = abs(date2 - date0)
     diff = abs(date1 - date2)
 
     # There should never be a days difference
     assert diff.days == 0
 
     # Since datetime.datetime.today() calls time.time(), and on some platforms
-    # that has 1 second accuracy, we should always be less than 2 seconds.
-    assert diff.seconds < 2
+    # that has 1 second accuracy, we compare this way
+    assert diff.seconds <= diff_python.seconds
 
 
 def test_chrono_system_clock_roundtrip():