[Event Homepage] Remove "Other" category from bar charts

[manuthecoder]

This pull request includes changes to simplify the logic in the run methods of BreakdownEngine services for merchants and users. The main change is the removal of the threshold condition and the "Other" category calculation, instead limiting the list to the top 7 items.

Simplification of logic in BreakdownEngine services:

• app/services/breakdown_engine/merchants.rb: Simplified the run method by removing the threshold condition and "Other" category calculation, and limiting the merchants list to the top 7 items.
• app/services/breakdown_engine/users.rb: Simplified the run method by removing the threshold condition and "Other" category calculation, and limiting the array list to the top 7 items.