Clarify introduction

While doing this exercise I was stuck on a test, when I noticed that this introduction doesn't fit the existing scenario. 

The test `Can identify multiple saddle points` has the following matrix:
`Matrix(List(List(4, 5, 4), List(3, 5, 5), List(1, 5, 4)))`

This is meant to produce `Set((0, 1), (1, 1), (2, 1)))`. This implies that in:
```
4 5 4
3 5 5
1 5 4
```

every tree in the middle column is valid; this contradicts the introduction that said that the tree must be **taller than**/**shorter than** the east-west and north-south line respectively.

Author: RafSobol

exercises/practice/saddle-points/.docs/introduction.md

@@ -7,5 +7,5 @@ You need to analyze each grid on the map to find good trees for your tree house.
 
 A good tree is both:
 
-- taller than every tree to the east and west, so that you have the best possible view of the sunrises and sunsets.
-- shorter than every tree to the north and south, to minimize the amount of tree climbing.
+- at least as tall as every tree to the east and west, so that you have the best possible view of the sunrises and sunsets.
+- at most as tall as every tree to the north and south, to minimize the amount of tree climbing.