xfstests: Remove 'su' from PATH

This needs to be coming from the setuid wrapper to work correctly.

pkgs/tools/misc/xfstests/default.nix

@@ -72,7 +72,7 @@ stdenv.mkDerivation {
       ln -s @out@/lib/xfstests/$f $f
     done
 
-    export PATH=${lib.makeBinPath [acl attr bc e2fsprogs fio gawk libcap lvm2 perl procps psmisc su utillinux which xfsprogs]}:$PATH
+    export PATH=${lib.makeBinPath [acl attr bc e2fsprogs fio gawk libcap lvm2 perl procps psmisc utillinux which xfsprogs]}:$PATH
     exec ./check "$@"
   '';