es6+beyond: ch2.md, fixing small word order issue

Small word order change.  Original text:
"is... very not ideal, performance wise."
Changed to read:
"is... not very ideal, performance wise."

es6 & beyond/ch2.md

@@ -2533,7 +2533,7 @@ var s1 = "abc\u0301d",
 [...s3.normalize()][2];			// "𝒞"
 ```
 
-**Warning:** Reminder of an earlier warning: constructing and exhausting an iterator each time you want to get at a single character is... very not ideal, performance wise. Let's hope we get a built-in and optimized utility for this soon, post-ES6.
+**Warning:** Reminder of an earlier warning: constructing and exhausting an iterator each time you want to get at a single character is... not very ideal, performance wise. Let's hope we get a built-in and optimized utility for this soon, post-ES6.
 
 What about a Unicode-aware version of the `charCodeAt(..)` utility? ES6 gives us `codePointAt(..)`: