Update arrays.md to remove outdated warning (#127)

Author: lens0021

docs/0.6.0-alpha/basic_syntax/arrays.md

@@ -24,8 +24,6 @@ echo groceries[1]
 // Outputs: banana
 ```
 
-> WARNING: As of right now (Amber alpha) the subscript syntax does not work with expressions. This means that we can't evaluate expressions like `foo()[0]` yet.
-
 We can also _echo_ an entire array:
 
 ```ab