Update instructions.md

Move generic instructions to the correct section.

Author: xanni

exercises/practice/square-root/.docs/instructions.md

@@ -9,5 +9,7 @@ Check out the Wikipedia pages on [square root][square-root] and [methods of comp
 
 Recall also that natural numbers are positive real whole numbers (i.e. 1, 2, 3 and up).
 
+It is possible to compute the square root of any natural number using only natural numbers in the computation.
+
 [square-root]: https://en.wikipedia.org/wiki/Square_root
 [computing-square-roots]: https://en.wikipedia.org/wiki/Methods_of_computing_square_roots