luarocks: remove unzip from setup-hook

The unzip variable is only set if it's an attribute and it's a
propagated input so it is already part of PATH.

pkgs/development/tools/misc/luarocks/setup-hook.sh

@@ -6,15 +6,11 @@ _tryRockSpec() {
 }
 
 _trySourceRock() {
-
     if ! [[ "$curSrc" =~ \.src.rock$ ]]; then return 1; fi
 
-    export PATH=${unzip}/bin:$PATH
-
     # luarocks expects a clean <name>.rock.spec name to be the package name
     # so we have to strip the hash
     renamed="$(stripHash $curSrc)"
     cp "$curSrc" "$renamed"
     luarocks unpack --force "$renamed"
 }
-