CONTRIBUTING.md in polyfill-0.6.0 vs CONTRIBUTING.md in polyfill-0.7.0

- old
+ new

@@ -10,11 +10,9 @@
 A list of changes can be found at:
 
  * https://raw.githubusercontent.com/ruby/ruby/v2_4_1/NEWS
  * https://raw.githubusercontent.com/ruby/ruby/v2_3_4/NEWS
  * https://raw.githubusercontent.com/ruby/ruby/v2_2_7/NEWS
- * https://raw.githubusercontent.com/ruby/ruby/v2_1_10/NEWS
- * https://raw.githubusercontent.com/ruby/ruby/v2_0_0_648/NEWS
 
 Specific changes can be found by going to the [Ruby bug/feature tracker].
 
 These are the steps that you'll need to follow for submitting code:
 