Fix unnecessary self in project.py

Signed-off-by: Shawn O. Pearce <sop@google.com>

project.py

@@ -1087,7 +1087,7 @@ class Project(object):
       self._InitAnyMRef(R_M + self.manifest.branch)
 
   def _InitMirrorHead(self):
-    self._InitAnyMRef(self, HEAD)
+    self._InitAnyMRef(HEAD)
 
   def _InitAnyMRef(self, ref):
     cur = self.bare_ref.symref(ref)