07-cond.md: Close Enough correction (#839)

`print(abs(a - b) < 0.1 * abs(b))` (and preceding Solution 2) leaves out the edge case where `a` is exactly 10% of `b`. This issue comes down to the interpretation of "within" 10%. Does a number within 10% of another number include the 10% value? 

Assume `b = 100` and `0.1 * b = 10`, then the value 10 is within 10% by definition since 10 is 10% of 100. Now set `a = 100 + 10 = 110` which is `b` plus 10% of `b`. Then `a - b = b + 0.1 * b - b = 0.1 * b`, which is within 10% of b.

The correct test is `abs(a - b) <= 0.1 * abs(b)` to account for this edge case.

Author: rshpeley

_episodes/07-cond.md

@@ -313,7 +313,7 @@ freeing us from having to manually examine every plot for features we've seen be
 > > a = 5
 > > b = 5.1
 > >
-> > if abs(a - b) < 0.1 * abs(b):
+> > if abs(a - b) <= 0.1 * abs(b):
 > >     print('True')
 > > else:
 > >     print('False')
@@ -323,7 +323,7 @@ freeing us from having to manually examine every plot for features we've seen be
 >
 > > ## Solution 2
 > > ~~~
-> > print(abs(a - b) < 0.1 * abs(b))
+> > print(abs(a - b) <= 0.1 * abs(b))
 > > ~~~
 > > {: .language-python}
 > >