dirstate: drop unused condition in `from_p2`

This conditional was added (by me) tentatively because "it seemed more
correct", but it is not used anywhere yet, and it is missing from the C and the
Rust implementation. So it seems more consistent to drop it for now.

This effectively backout f94cc63df859c

Differential Revision: https://phab.mercurial-scm.org/D11510

mercurial/pure/parsers.py

@@ -336,7 +336,7 b' class DirstateItem(object):'
         """
         if not self._wc_tracked:
             return False
-        return self._clean_p2 or (not self._p1_tracked and self._p2_tracked)
+        return self._clean_p2
 
     @property
     def from_p2_removed(self):