Fix copyWorkplane (#1770)

* Fix copyWorkplane

* Back to T

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Co-authored-by: AU <adam-urbanczyk@users.noreply.github.com>

Author: bfleischhacker

cadquery/cq.py

@@ -664,7 +664,7 @@ def copyWorkplane(self, obj: T) -> T:
         :type obj: a CQ object
         :returns: a CQ object with obj's workplane
         """
-        out = obj.__class__(obj.plane)
+        out = copy(obj)
         out.parent = self
         out.ctx = self.ctx
         return out