aur: Use tar file for polybar package

We provide the polybar.tar as part of our release process so it is more
efficient to let users build directly from the uploaded archive

contrib/polybar.aur/PKGBUILD

@@ -22,11 +22,10 @@ optdepends=("alsa-lib: alsa module support"
 makedepends=("cmake" "git" "python" "python2" "pkg-config")
 conflicts=("polybar-git")
 install="${pkgname}.install"
-source=("${pkgname}::git+${url}.git#tag=${pkgver}")
-md5sums=("SKIP")
+source=(${url}/releases/download/${pkgver}/polybar.tar)
+sha256sums=('647dde8fbf6690138b354bf538d1d97ba8c1743ff22314af4ee085e06a1f506a')
 
 prepare() {
-  git -C "${pkgname}" submodule update --init --recursive
   mkdir -p "${pkgname}/build"
 }