fix(iOS): DAUTests.testMondayOfCurrentWeekFormatted() unit test

[StephenHeaps]

• Update unit test to grab the year directly from gregorian calendar using DateComponents so the year shouldn't need updated.

Resolves brave/brave-browser#43117
Resolves brave/brave-browser#43132

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Test Plan:

Run DAUTests.testMondayOfCurrentWeekFormatted()

[kylehickinson]

Wouldn't this fail if the monday of the current week is in a previous year? For example from 2024-2025, if the current date was Jan 1 2025 (Wed), the monday of the week would be Dec 30 2024

[StephenHeaps]

Hmm yeah I think you're right since we're looking backwards. Maybe better to check against gregorianCalendarYear - 1 for that case, ex:
XCTAssert(year >= (gregorianCalendarYear - 1) && year <= gregorianCalendarYear)

[kylehickinson]

Either that or use a fixed date for generating the current monday (which honestly may be safer anyways)

[brave-builds]

Released in v1.75.150