UI: Capitalize "Python" in UI messages, improve a few others

- "... (matches pythons ...)": capitalize and use possessive ('s).
- "Layer Proxy Protection": replace proxy by override, following 2.80.
- "Enable Plane Trim": expand description.
- "Make curve path children to rotate along the path": remove "to".
- "Option for curve-deform: make deformed child to stretch along
  entire path": remove "to".
- "... apply the curve radius with path following it and deforming":
  rephrase unclear description.
- "Custom light falloff curve" : unrelated to lights, used in Grease
  Pencil modifiers.
- "Grease Pencil layer assigned to the generated strokes": rephrase
  because a GP stroke is assigned to a layer, not the other way
  around.
- "Attribute domain where the attribute domain is stored in the
  simulation state": remove second "domain" (typo).

Pull Request: blender/blender#107916

source/blender/python/generic/idprop_py_api.c

@@ -1553,7 +1553,7 @@ static PyObject *BPy_IDGroup_update(BPy_IDProperty *self, PyObject *value)
 PyDoc_STRVAR(BPy_IDGroup_to_dict_doc,
              ".. method:: to_dict()\n"
              "\n"
-             "   Return a purely python version of the group.\n");
+             "   Return a purely Python version of the group.\n");
 static PyObject *BPy_IDGroup_to_dict(BPy_IDProperty *self)
 {
   return BPy_IDGroup_MapDataToPy(self->prop);