ENYO-3934: Ensure that browser language's region identifier is formatted correctly.

Issue
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In certain browsers such as Safari, the browser-reported language is returned in a format where the region identifier is lowercase, i.e. `en-us`. This causes issues in properly utilizing the default locale for ilib functions.

Fix
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When using the browser language, we properly format the region identifier portion of the string by making it uppercase.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>