Change cooldown key to default-days in dependabot config (#1902)

Co-authored-by: Jan Calanog <[email protected]>

Author: v1v

.github/dependabot.yml

@@ -13,7 +13,7 @@ updates:
     directories:
       - '**/*'
     cooldown:
-      days: 14
+      default-days: 14
     schedule:
       interval: 'weekly'
       day: 'monday'