chia: fix spurious permissions warning

Fixes #145111

pkgs/applications/blockchains/chia/default.nix

···
     substituteInPlace setup.py \
       --replace "==" ">="
 
-    ln -sf ${cacert}/etc/ssl/certs/ca-bundle.crt mozilla-ca/cacert.pem
+    cp ${cacert}/etc/ssl/certs/ca-bundle.crt mozilla-ca/cacert.pem
   '';
 
   nativeBuildInputs = [