data: adjust names of fallback icon theme

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/c6e634c272fb4086898d7bb0bdc89b3d/

Change-Id: Ia84ef5b098d7f316bd25085566290c60e9af50fa
Merge "data: adjust names of fallback icon theme"