fix little typo in arrow function argument's remove duplicate code section

Author: raerpo

README.md

@@ -395,7 +395,7 @@ generic functions quite easy. Take advantage of that!
 **Bad:**
 ```javascript
 function showDeveloperList(developers) {
-  developers.forEach(developers => {
+  developers.forEach(developer => {
     var expectedSalary = developer.calculateExpectedSalary();
     var experience = developer.getExperience();
     var githubLink = developer.getGithubLink();