GHA workflow for l10n failing due to missing secret

[rmunn]

The workflow added in #326 has been failing to run because secrets.CROWDIN_PAT is empty. See this build log where the crowdin download --all -T ${{ secrets.CROWDIN_PAT }} step is turning into crowdin download sources -T due to the missing CROWDIN_PAR secret, which then results in the crowdin tool complaining about a missing required parameter for the -T option.