matrix: use correct override

hosts/matrix/default.nix

@@ -13,10 +13,9 @@
   nixpkgs.overlays = [
     (final: prev: {
       # NOTE: using config.services.matrix-synapse.package does not work because it does not override the matrix-synapse used in matrix-synapse.plugins.matrix-synapse-ldap3
-      matrix-synapse = prev.matrix-synapse.overrideAttrs (_: {
+      matrix-synapse = prev.matrix-synapse.overridePythonAttrs (_: {
         # fail and take a good amount of time
         doCheck = false;
-        doInstallCheck = false;
       });
     })
   ];