Update DIRECTORY.md

Author: domix80

DIRECTORY.md

@@ -153,8 +153,6 @@
     * [Sol2](https://github.com/TheAlgorithms/Ruby/blob/master/project_euler/problem_004/sol2.rb)
   * Problem 005
     * [Sol1](https://github.com/TheAlgorithms/Ruby/blob/master/project_euler/problem_005/sol1.rb)
-  * Problem 010
-    * [Sol1](https://github.com/TheAlgorithms/Ruby/blob/master/project_euler/problem_010/sol1.rb)
   * Problem 020
     * [Sol1](https://github.com/TheAlgorithms/Ruby/blob/master/project_euler/problem_020/sol1.rb)
   * Problem 021