fixup! In __buildout_signature__, fix missing parts that are pulled by recipes' __init__

To support versions 33.1.1 and 36.6.1 of setuptools.

src/zc/buildout/tests.py

@@ -2145,11 +2145,11 @@ def test_part_pulled_by_recipe():
     ...
     [b]
     __buildout_installed__ = 
-    __buildout_signature__ = recipes-c79aac86a90182467ce2fdae8b56eb1c c:...
+    __buildout_signature__ = recipes-... c:...
     ...
     [a]
     __buildout_installed__ = 
-    __buildout_signature__ = recipes-c79aac86a90182467ce2fdae8b56eb1c b:...
+    __buildout_signature__ = recipes-... b:...
     ...
     """