Remove i686 from arch=()

FTR, commands used to change arch=() and then verify the changes:

$ sed -Ei "/^arch=/{s/ *?['\"]?i686['\"]? *?//;s/ *$//}" */*/PKGBUILD*

$ grep -r i686 * | grep arch= | grep -v repos

$ svn diff | grep -A 1 ^-[^-] | grep -v -- -- | cut -c2- |
  while IFS=$'\n' read -r l1; IFS=$'\n' read -r l2; do
    echo "$l1 -> $l2"
  done | sort -u

PKGBUILD

@@ -8,7 +8,7 @@ pkgrel=21
 pkgdesc="Orphan Instances for \'Data.Vector\'"
 url="https://github.com/ekmett/vector-instances"
 license=("custom:BSD3")
-arch=('i686' 'x86_64')
+arch=('x86_64')
 depends=('ghc-libs' "haskell-comonad" "haskell-hashable" "haskell-keys" "haskell-pointed"
          "haskell-semigroupoids" "haskell-semigroups" "haskell-vector")
 makedepends=('ghc')