Merge case 30 to "two digits convert to one word"
There are two possible transformations in this commit
1. Test: adding cases for all two digits convert to one word (30..90)
    TPP: constant -> constant+ (adding more key-value pairs into NUMBER_TO_ONE_WORD map). Same as before, I'm not sure we should categorize this transformation as such. A transformation to add more key-value pairs into a map could be categorized as:
    1. constant -> constant+
    2. statement -> statements
    3. a new transformation not in current TPP list
 2. Test: 31 and 32
     TPP: first is unconditional -> if (number == 31). And the new execution path is a nil -> constant transformation.
     And then (by case 32), constant (expression) -> function (20 -> NUMBER_TO_ONE_WORD.floorKey(number)), a quite low priority transformation.

 I'd like to follow the first transformation here and see what happens later.
Revert the cases 31 and 32 and code to implement them