po4a: disable tests

After a `gettext-0.25` update the tests started failing for CR/LF files:
https://github.com/mquinson/po4a/issues/580

Let's disable the on all platforms.

pkgs/development/perl-modules/Po4a/default.nix

@@ -100,7 +100,9 @@ buildPerlPackage rec {
   # https://git.alpinelinux.org/aports/tree/main/po4a/APKBUILD#n11
   #
   # Disabling tests on Darwin until https://github.com/NixOS/nixpkgs/issues/236560 is resolved.
-  doCheck = (!stdenv.hostPlatform.isMusl) && (!stdenv.hostPlatform.isDarwin);
+  #
+  # Disabling tests on linux (gettext-0.25): https://github.com/mquinson/po4a/issues/580
+  doCheck = false;
 
   checkPhase = ''
     export SGML_CATALOG_FILES=${docbook_sgml_dtd_41}/sgml/dtd/docbook-4.1/docbook.cat