python3Packages.spacy: add passthru test

I have been using the main example of the spaCy web page for testing
updates of spacy (and its transitive dependencies). Let's convert this
into a proper test to take out manual testing.

pkgs/development/python-modules/spacy/default.nix

@@ -1,5 +1,6 @@
 { lib
 , buildPythonPackage
+, callPackage
 , fetchPypi
 , pythonOlder
 , pytest
@@ -64,6 +65,8 @@ buildPythonPackage rec {
 
   pythonImportsCheck = [ "spacy" ];
 
+  passthru.tests = callPackage ./annotation-test {};
+
   meta = with lib; {
     description = "Industrial-strength Natural Language Processing (NLP) with Python and Cython";
     homepage = "https://github.com/explosion/spaCy";