DOCSP-34891: Add admonition to mention users must catch errors raised by withTransaction() callback (mongodb#922)

(cherry picked from commit dc66c14)

Author: mcmorisi

source/fundamentals/transactions.txt

@@ -170,6 +170,11 @@ if a callback you pass to the ``withTransaction()`` method returns the
 document ``{ hello: "world" }``, then the ``withTransaction()`` method
 also returns that document.
 
+.. important::
+   
+   To avoid infinite looping errors, ensure that the callback you pass to
+   the ``withTransaction()`` method catches any errors that it raises.
+
 When you use the Convenient Transaction API, you
 can propagate return values from the callback as the return values of
 the ``withTransaction()`` and ``withSession()`` methods to