swift: remove conditional for lucid

We have no lucid Swift clusters anymore and there's no going back, so
cleanup the conditional where it installed SwiftMedia into Python 2.6
paths. While at it, remove the outdated comment about SwiftMedia's
canonical place; puppet is its canonical place nowadays.

Change-Id: I4e914d7f6818ad6cfa23023377d5968a5d72d04e