Customize “older posts” message

On pages for posts (blog), I replaced the French links “Articles plus anciens” (older posts) and “Articles plus récents” (newer posts) by “Page précédente” (Previous page) and “Page suivante” (Next page) by modifying the files fr_FR.po and fr_FR.mo. But these files are systematically overwritten by all WordPress updates. I haven’t found any effective method to turn off automatic updates so these files are updated automatically and regularly. What solution then to permanently update these older posts / newer posts links with the Dyad theme? I already have a child theme.

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