docs!: Remove doc tutorial on depend.txt (it will need rewriting)

Author: AltGr

docs/howto-write-exercises.md

@@ -65,9 +65,3 @@ get the files for the second step, and so on and so forth.
 [Step 6 : Grading functions for variables](tutorials/step-6.md)
 
 [Step 7 : Modifying the comparison functions (testers) with the optional arguments [~test], [~test_stdout], [~test_stderr]](tutorials/step-7.md)
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-[Step 8 : Reusing the grader code](tutorials/step-8.md)
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-- Separating the grader code
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-[Step 9 : Introspection of students code](tutorials/step-9.md)