Revert "Enable JPG thumbnail chaining on all wikis except commons"

This reverts commit bc227c0fd130832e362491a6f4cba9da24b74f90.

Change-Id: I129ca70eb2a5e4c644779b4ecc0a20f6d37868e9
Merge "Revert "Enable JPG thumbnail chaining on all wikis except commons""