fix one word

Author: jianminchen

Small Example From Google talk/readme.md

@@ -21,4 +21,4 @@
 
 Sept. 7, 2018
 
-Add a new folder with those three examples, one is conditional version, naive one, break Single responsiblity principle; second one is to separate OpNode and ValueNode; third one is to apply polymorphic solution, for each operator, there is one class for the oeprator. 
+Add a new folder with those three examples, one is conditional version, naive one, break Single responsiblity principle; second one is to separate OpNode and ValueNode; third one is to apply polymorphic solution, for each operator, there is one class for the operator.