Fix typo README.md

Fix typo on README.md xD

Author: art-1st

README.md

@@ -168,7 +168,7 @@ stepFunctions:
       dependsOn:
         - DynamoDBTable
         - KinesisStream
-        - CUstomIamRole
+        - CustomIamRole
       tags:
         Team: Atlantis
   activities:
@@ -1696,4 +1696,4 @@ stepFunctions:
 
 plugins:
   - serverless-step-functions
-```
+```