[Cs3] updated associative containers slides, no onordered containers on the first midterm

[Mikhail Nesterenko]

CS3 students,

I updated the associative containers slides with the typos and other
minor issues we found during today's lecture.

Also, a reminder. The unordered containers (hashmaps) are not on this
midterm. So you do not need to study them or prepare study guides for
them.

Thank you,
-- 
Mikhail