Fix localization in the profile error dialog

We have a patch to provide more specific error messages when we fail to open the profile (e.g., read-only directory).

But the localization on this patch seems not to work:

chmod -R a-w tor-browser
LC_ALL=it_IT.UTF-8 ./start-tor-browser -v

Console messages are in Italian as expected:

cp: impossibile creare il file regolare '../start-tor-browser.desktop': Permesso negato
sed: impossibile aprire il file temporaneo ../sednedqWP: Permesso negato
sed: impossibile aprire il file temporaneo ../sedCMdt8H: Permesso negato
sed: impossibile aprire il file temporaneo ./sedKdfnQ8: Permesso negato
sed: impossibile aprire il file temporaneo ../sedaAd4yu: Permesso negato

But our error message is in English.

I think the problem is that we try to infer the language from intl.locale.requested, which is empty because we use multi-lingual builds (and any customization won't be fetched until we have a profile).

The alternative is to entirely drop this patch, if we think it's not worth to maintain it.