Revert "Correct semigroups conditional version bounds (#134)"
Revert "Correct semigroups conditional version bounds (#134)"

This reverts commit 1445eddb2ec015e1e693050a8e3b9e1fe14c51d6.

This is wholly unnecessary, since the version number `8.0` is less than
`8.0.x`, as pointed out in
https://github.com/haskell/vector/pull/134#issuecomment-240328937

dolio/vector