gh-36076: Remove deprecated parameter circular from method `is_planar`
    
Remove deprecated parameter `circular` from method `is_planar`. The
deprecation was introduced in #33759.

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- [ ] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.

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URL: #36076
Reported by: David Coudert
Reviewer(s): Frédéric Chapoton

Author: Release Manager

src/sage/graphs/planarity.pyx

@@ -30,7 +30,7 @@ cdef extern from "planarity/graph.h":
     cdef int gp_SortVertices(graphP theGraph)
 
 
-def is_planar(g, kuratowski=False, set_pos=False, set_embedding=False, circular=None):
+def is_planar(g, kuratowski=False, set_pos=False, set_embedding=False):
     r"""
     Check whether ``g`` is planar using Boyer's planarity algorithm.
 
@@ -55,8 +55,6 @@ def is_planar(g, kuratowski=False, set_pos=False, set_embedding=False, circular=
       combinatorial embedding returned (see
       :meth:`~sage.graphs.generic_graph.GenericGraph.get_embedding`)
 
-    - ``circular`` -- deprecated argument
-
     EXAMPLES::
 
         sage: G = graphs.DodecahedralGraph()
@@ -98,10 +96,6 @@ def is_planar(g, kuratowski=False, set_pos=False, set_embedding=False, circular=
             ....:     assert (hasattr(G, '_pos') and G._pos is not None) == set_pos, (set_embedding, set_pos)
 
     """
-    if circular is not None:
-        from sage.misc.superseded import deprecation
-        deprecation(33759, 'the circular argument of is_planar is deprecated and has no effect')
-
     if set_pos and not g.is_connected():
         raise ValueError("is_planar() cannot set vertex positions for a disconnected graph")