[fixup] Fix zc.recipe.egg tests

Fixup "[fix] Fix working set sorting".

Some zc.recipe.egg tests were never adapted accordingly.

zc.recipe.egg_/src/zc/recipe/egg/working_set_caching.rst

@@ -27,6 +27,7 @@ Here's an example:
     ...     distributions=['zc.recipe.egg', 'demo<0.3'],
     ...     eggs_dir=eggs_dir,
     ...     develop_eggs_dir=develop_eggs_dir,
+    ...     buildout_dir=sample_buildout,
     ...     index=link_server,
     ... )
     Getting...
@@ -52,6 +53,7 @@ built only once.
     ...     distributions=['demo>=0.1'],
     ...     eggs_dir=eggs_dir,
     ...     develop_eggs_dir=develop_eggs_dir,
+    ...     buildout_dir=sample_buildout,
     ...     offline=True,
     ... )
     >>> ws_args_2 = dict(ws_args_1)