Remove some strings from Localizable.strings

[dstillman]

I've uploaded strings to Transifex, but I did notice some strings that don't really need to be there. Anything that's an internal error, or that people couldn't possibly fix themselves and really just needs to exist so people have an error message to post to the forums, can be hard-coded. No need to make translators localize them.

Here are some that I deleted locally before uploading to Transifex, but there are probably others:

-"beta_wipe_title" = "Resync Required";
-"beta_wipe_message" = "Due to a beta update, your data must be redownloaded from zotero.org.";
-"errors.shareext.parsing_error" = "Error parsing translator response";
-"errors.shareext.incompatible_item" = "No data returned";
-"errors.shareext.javascript_failed" = "JS call failed";
-"errors.shareext.missing_base_files" = "Translator missing";
-"errors.shareext.missing_file" = "Could not find file to upload";
-"errors.shareext.background_uploader_failure" = "Background uploader not initialized";
-"errors.logging.content_reading" = "Log files could not be found";
-"errors.translators.bundle_reset" = "Could not load bundled translators.";

Would be good to remove any other sooner rather than later to keep people from localizing them unnecessarily.

[dstillman]

Actually, if strings might get shown to users at all, better than hard-coding them would just be to move them to a separate .strings file that we don't upload to Transifex. (Not sure if other locales can fall back to en-US just for a single file. If not, we'd need to copy it to all other locales at build time.)