Remove 'Edit in Pocket Paint' from context menu
Remove 'Edit in Pocket Paint' from overflow menu
Remove unused string edit_in_pocket_paint

Although edit_in_pocket_paint is no longer used in Catroid it is still
used in the tests (LookFragmentTest) for ensuring that the string is no
longer visible. Remove variable from strings.xml and hardcode 'Edit in
Pocket Paint' in LookFragmentTest.
Change 'assertEquals' to 'assertFalse'