Clarify ambiguity in 02/Chipotle steps 4 and 5

[desmondcheongzx]

Update revenue calculation task in 01_Getting_&_Knowing_Your_Data/Chipotle
to be consistent with the understanding that item_price = quantity * price per item.

Clarify step 4 in 02_Filtering_&_Sorting/Chipotle to ask for all items
where the price per item is able to be greater than $10. This is to
accomodate the cases where an item usually costs less than $10, but with
certain choice_description it is able to cost more than $10. To
simplify the task, we simply include such cases and provide the user
with an example.

Similarly, for step 5 in 02_Filtering_&_Sorting/Chipotle, items can
have multiple prices depending on the choice_description they are paired
with. To remove the ambiguity, update the task to ask for the price
of each unique combination of item_name and choice_description.

[desmondcheongzx]

#62 and #65 both raise questions about the multiple interpretations for calculating the price of an item. I believe this confusion is linked to an earlier task in 01_Getting_&_Knowing_Your_Data/Chipotle where we are asked to find the revenue for this period. The previous solution involved multiplying 'quantity' with 'item_price' even though 'item_price' already implicitly multiplies the quantity with the price per item, as mentioned in #65:

Example:
order _id | quantity | item_name | choice_description | item_price
9 | 2 | Canned Soda | [Sprite] | $2.18
14 | 1 | Canned Soda | [Dr. Pepper] | $1.09

Making this task consistent with the later task, and adding some additional clarification and examples, could make the task clearer and remove friction from the learning process.