Revert "Fixing core reconstruction" (#789)

* Revert "better leakage parameter calculation (#783)"

This reverts commit 20c74be.

* Revert "Fixing core reconstruction (#777)"

This reverts commit 5d4cd37.

ctapipe/reco/HillasReconstructor.py

@@ -327,9 +327,7 @@ def estimate_core_position(self):
             # circle.norm to the ground gives higher weight to planes
             # perpendicular to the ground and less to those that have
             # a steeper angle
-            norm = circle.norm.copy()
-            norm[1] = - norm[1]
-            A[i] = circle.weight * norm[:2]
+            A[i] = circle.weight * circle.norm[:2]
             # since A[i] is used in the dot-product, no need to multiply the
             # weight here
             D[i] = np.dot(A[i], circle.pos[:2])