Rename method top in lab9 (words) to clarify its purpose

[MaximilianUggla]

Multiple students stated that the top was either the most time-consuming or confusing or part of the lab. However, they said once they understood what it should do, they did not find the method particularly hard to implement. The lab could benefit from renaming top.

Examples for new name:
mostRecurringWords
mostCommonWords
nMostFrequent