Delete links

Students click on links and browser opens up. This causes exam app exit.

subjects/printdigits.en.md

@@ -2,9 +2,9 @@
 
 ### Instructions
 
-Write a [program](TODO-LINK) that prints the decimal digits in ascending order (from `0` to `9`) on a single line.
+Write a program that prints the decimal digits in ascending order (from `0` to `9`) on a single line.
 
-A line is a sequence of characters preceding the [end of line](https://en.wikipedia.org/wiki/Newline) character (`'\n'`).
+A line is a sequence of characters preceding the end of line character (`'\n'`).
 
 ### Usage