Revert "Use localized namespace name in embed wikitext"

Mark pointed out that using localized namespace names would cause 
problems when users try to reuse images across wikis with different 
content language. Reverting for now.

This reverts commit 59b8e5c82acad1bf094519d3635c25331000475b.

Bug: 64710
Change-Id: I4b8b46871a1c80bce20e4017aa8adcfe3041bb4a
Merge "Revert "Use localized namespace name in embed wikitext""