Cleanup the PKGBUILD

https://wiki.archlinux.org/title/Arch_package_guidelines says empty
lines should be removed.

PKGBUILD

@@ -2,23 +2,11 @@
 pkgname=liboprf
 pkgver=0.9.3
 pkgrel=1
-epoch=
 pkgdesc="library providing OPRF and Threshold OPRF based on libsodium"
 arch=(x86_64)
 url="https://github.com/stef/liboprf"
 license=('LGPL-3.0-or-later')
-groups=()
 depends=('libsodium')
-makedepends=()
-checkdepends=()
-optdepends=()
-provides=()
-conflicts=()
-replaces=()
-backup=()
-options=()
-install=
-changelog=
 source=("${pkgname}-${pkgver}.tar.gz::https://github.com/stef/$pkgname/archive/refs/tags/v$pkgver.tar.gz"
 	"https://github.com/stef/$pkgname/releases/download/v$pkgver/$pkgname-$pkgver.tar.gz.asc")
 noextract=()
@@ -26,10 +14,6 @@ b2sums=('628a6e9549ba688ade57b8b07a9cb488a3e750aabef0619141f16f98c7bf99d56185e0f
         'SKIP')
 validpgpkeys=('AABDE16CB6AF5CD10A28DFF2970DEB6694D50988')
 
-prepare() {
-	cd "$pkgname-$pkgver"
-}
-
 build() {
 	cd "$pkgname-$pkgver"/src
 	make PREFIX=/usr