I18N: Add context for the `Archives` string introduced in [45651] as a file...

I18N: Add context for the `Archives` string introduced in [45651] as a file type heading, to disambiguate from other types of archives.

Props alexclassroom.
Fixes #48259.
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git-svn-id: https://core.svn.wordpress.org/trunk@46235 1a063a9b-81f0-0310-95a4-ce76da25c4cd