A file has contracted a case of bad language code upon use of SVG Translate Tool. The revision in question is https://upload.wikimedia.org/wikipedia/commons/archive/d/dc/20201231085805%21Research_design_and_evidence_-_Capho.svg which has `systemLanguage="zh_HANS"` (with an underscore); it works after being changed to https://upload.wikimedia.org/wikipedia/commons/d/dc/Research_design_and_evidence_-_Capho.svg which has `systemLanguage="zh-Hans"` (with a hyphen).
To reproduce, just choose 中文（简体）as the target language. Typing "zh" in the search box helps.
The language code should be normalized to all lowercase and with a hyphen separator, regardless of what format is already in the file.
Acceptance criteria:
* No file being output from the tool should be able to have a `systemLanguage` attribute in the wrong format.