Update the template-cleanup readme (kotlin-hands-on#10)

Author: mattcorbin

.github/template-cleanup/README.md

@@ -13,7 +13,7 @@ If you're stuck with Kotlin-specific questions or anything related to this templ
 
 [^aoc]:
     [Advent of Code][aoc] – An annual event of Christmas-oriented programming challenges started December 2015.
-    Every year since then, beginning on the first day of December, a programming puzzle is published every day for twenty-four days.
+    Every year since then, beginning on the first day of December, a programming puzzle is published every day for twenty-five days.
     You can solve the puzzle and provide an answer using the language of your choice.
 
 [aoc]: https://adventofcode.com