file: Drop string concatenation to make gettext work properly

Ondrej Holy requested to merge wip/oholy/gettext-fix into master

The commit 35647f24 fixed build on 32-bit architectures using the relevant format string, but gettext isn't able to extract the text now due to string concatenation. Let's use the format string outside of the ngettext function to fix the issue.

Related: !940 (merged)

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