OJT21-52: Fix typo in README.md

@@ -6,5 +6,5 @@
             # frozen_string_literal: true
             # frozen_string_literal: true
 
 
             ENV['MYSQL_USERNAME'] = 'your_user_name'
             ENV['MYSQL_USERNAME'] = 'your_user_name'
-            ENV['MYSQL_USERNAME'] = 'your_password'
+            ENV['MYSQL_PASSWORD'] = 'your_password'
     }
     }