fix: archive past KDD cups and update main resource link to current year (#6770)

* archive past KDD cups and update link main resource to current year

* Remove KDD Cup

Author: davorpa

Diff for: more/problem-sets-competitive-programming.md

@@ -68,7 +68,6 @@
 * [CrowdANALYTIX](https://www.crowdanalytix.com/community)
 * [DrivenData](https://www.drivendata.org)
 * [Kaggle](https://www.kaggle.com)
-* [KDD Cup](https://www.kdd.org/kdd2019/kdd-cup)
 
 
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