Updated B3MultiFormat constructor docstring.

Author: vitaly-krugl

propagator/opentelemetry-propagator-b3/src/opentelemetry/propagators/b3/__init__.py

@@ -108,16 +108,15 @@ def __init__(
             sampling_arbiter: typing.Optional[PropagatorSamplingArbiterInterface] = None):
         """
         NOTE: The B3 spec calls for "defer the decision to the receiver" whenever
-        explicit sampling information is absent from the carrier; this concept
-        does not translate to SpanContext, so we will invoke the Propagator
-        Sampling Arbiter as tie-breaker whenever sampling information is absent
-        from the carrier. (https://github.com/openzipkin/b3-propagation)
+        explicit sampling information is absent from the carrier; in this scenario
+        we will invoke the given Propagator Sampling Arbiter to make the sampling
+        decision. (https://github.com/openzipkin/b3-propagation)
 
         :param sampling_arbiter: A user-supplied arbiter instance to decide the sampled state
             for our `extract()` method whenever sampling information is absent from carrier.
-            If None, will fall back to the legacy behavior for backward compatibility: defaults
-            decision to enabled for single-header and to disabled for multi-header (in the
-            event explicit sampling information is absent from the carrier)
+            If None, falls back to the legacy behavior for backward compatibility: defaults
+            decision to Accept for single-header and to Deny for multi-header (in the
+            event explicit sampling information is absent from the carrier).
         """
         super().__init__()
         if sampling_arbiter is not None: