Update UI tests for Traffic tab

[guarani]

We have some minimal tests in StatsTests that need to be updated here when the Traffic tab is enabled.

[staskus]

Implemented tests (#22703) were date-dependant (1c83a97). The date that was associated with February, are now associated with March (see ./API-Mocks/WordPressMocks/src/main/assets/mocks/mappings/wpcom/stats/stats_visits-month.json). Tests require improvement.

[guarani]

I moved this issue off the Traffic project because the UI Tests for Traffic that remain verify that the Traffic screen is there:

WordPress-iOS/WordPress/UITests/Tests/StatsTests.swift

Line 40 in f7a950d

func testTrafficYearsStatsLoadProperly() throws {

I think that's sufficient for this project. I've put this on the "Address remaining bugs" project to follow up on later.

[staskus]

No longer relevant for now.