Remove SdssShape from dipoleFit

DipoleFitTask doesn't use shape measurements, and SdssShape doesn't
handle negative sources well; detectAndMeasure uses shapeHsm, which is
better.

python/lsst/ip/diffim/dipoleFitTask.py

@@ -109,15 +109,14 @@ def setDefaults(self):
                               "base_PixelFlags",
                               "base_SkyCoord",
                               "base_PsfFlux",
-                              "base_SdssShape",
                               ]
         # Only measure the apertures we need to report in the alert stream.
         self.plugins["base_CircularApertureFlux"].radii = [12.0]
 
         self.slots.calibFlux = None
         self.slots.modelFlux = None
         self.slots.gaussianFlux = None
-        self.slots.shape = "base_SdssShape"
+        self.slots.shape = None
         # This will be switched to "ip_diffim_DipoleFit" as this task runs.
         self.slots.centroid = "base_SdssCentroid"
         self.doReplaceWithNoise = False