Deprecate distorted WCS method

This was replaced with a system that uses the camera geometry directly when
raw files are read in, which is more reliable.

python/lsst/afw/geom/wcsUtils/wcsUtilsContinued.py

@@ -22,6 +22,8 @@
 
 __all__ = ["getSipMatrixFromMetadata", "makeDistortedTanWcs", "computePixelToDistortedPixel"]
 
+from deprecated.sphinx import deprecated
+
 import lsst.geom
 from ..transformFactory import linearizeTransform, makeTransform
 from ..skyWcs import makeModifiedWcs
@@ -58,7 +60,8 @@ def getSipMatrixFromMetadata(metadata, name):
         arr.shape = (1, 1)
     return arr
 
-
+@deprecated(reason="Camera geometry-based SkyWcs are now set when reading raws. To be removed after v20.",
+            category=FutureWarning)
 def makeDistortedTanWcs(tanWcs, pixelToFocalPlane, focalPlaneToFieldAngle):
     """Compute a WCS that includes a model of optical distortion.