Update check your other device copy

[MiSikora]

Task/Issue URL: https://app.asana.com/1/137249556945/task/1218362898011218?focus=true
Tech Design URL (if applicable): N/A
API Proposals URL(s) (if applicable): N/A

Description

Copy update.

Steps to test this PR

QA optional.

UI changes

N/A

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Note

Low Risk
Single English string punctuation change with no behavioral impact.

Overview
Updates the Simplified Sync pairing screen headline copy for the “waiting on other device” state: sync_simplified_pairing_headline_check_other_device now ends with a period (“Check your other device.” instead of “Check your other device”).

No logic or layout changes—only the default strings-sync.xml English string used when pairing is waiting (e.g. in ProcessSyncCodeActivity).

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