python3Packages.python-lsp-server: Add undeclared but necessary optional dependency

This is no longer implicitly provided by python3Packages.autopep8, causing tests to fail.
Upstream issue: https://github.com/python-lsp/python-lsp-server/issues/260

pkgs/development/python-modules/python-lsp-server/default.nix

@@ -23,6 +23,7 @@
 , rope
 , setuptools
 , setuptools-scm
+, toml
 , ujson
 , websockets
 , whatthepatch
@@ -79,6 +80,7 @@ buildPythonPackage rec {
       pyflakes
       pylint
       rope
+      toml
       whatthepatch
       yapf
     ];