Add missing retryable write case to pseudo code

The pseudo code example for executing retryable write commands was
missing the case below:

- CSOT is not enabled and one retry was attempted.

This corrects the pseudo code to unify it with the prose description.

Related to: DRIVERS-1807

source/retryable-writes/retryable-writes.rst

@@ -513,6 +513,11 @@ The above rules are implemented in the following pseudo-code:
  if (timeoutMS != null && isExpired(timeoutMS) {
  throw previousError;
  }
+
+ /* If CSOT is not enabled attempt one retry before giving up. */
+ if (timeoutMS == null) {
+ return executeCommand(server, retryableCommand);
+ }
  }
  }