Scheduler: mask the whole recurrence end date in visual tests (25_2)

[sjbur]

Summary

• Backport of Scheduler: mask the whole recurrence end date in visual tests #35687 to 25_2.
• The recurrence form On date defaults to today. The fluent masks for the weekly and readonly screenshots stopped one pixel above that text, so the comparison fails when the date glyphs change.
• The masks now cover the whole interior of that date box. Daily, hourly, monthly, yearly and the other recurrence-form masks already cover the text.

Test plan

• recurrence form in Weekly frequency passes on fluent.blue.light
• recurrence form readonly state passes on fluent.blue.light