fix typo about SamplingRule class

Author: hassaku63

aws_xray_sdk/core/sampling/local/sampling_rule.py

@@ -5,7 +5,7 @@
 
 class SamplingRule:
     """
-    One SamolingRule represents one rule defined from local rule json file
+    One SamplingRule represents one rule defined from local rule json file
     or from a dictionary. It can be either a custom rule or default rule.
     """
     FIXED_TARGET = 'fixed_target'