Remove Beam cleanup (#6414)

Beam cleanup is handled through the Beam finalization method.

spacy/syntax/_beam_utils.pyx

@@ -304,27 +304,3 @@ def get_gradient(nr_class, beam_maps, histories, losses):
                 grads[j][i, clas] += loss
                 key = key + tuple([clas])
     return grads
-
-
-def cleanup_beam(Beam beam):
-    cdef StateC* state
-    # Once parsing has finished, states in beam may not be unique. Is this
-    # correct?
-    seen = set()
-    for i in range(beam.width):
-        addr = <size_t>beam._parents[i].content
-        if addr not in seen:
-            state = <StateC*>addr
-            del state
-            seen.add(addr)
-        else:
-            raise ValueError(Errors.E023.format(addr=addr, i=i))
-        addr = <size_t>beam._states[i].content
-        if addr not in seen:
-            state = <StateC*>addr
-            del state
-            seen.add(addr)
-        else:
-            raise ValueError(Errors.E023.format(addr=addr, i=i))
-
-

spacy/syntax/nn_parser.pyx

@@ -373,8 +373,6 @@ cdef class Parser:
             self.moves.finalize_doc(doc)
             for hook in self.postprocesses:
                 hook(doc)
-        for beam in beams:
-            _beam_utils.cleanup_beam(beam)
 
     def transition_states(self, states, float[:, ::1] scores):
         cdef StateClass state
@@ -527,9 +525,6 @@ cdef class Parser:
             else:
                 model.backprops.append((ids, d_vector, bp_vectors))
         model.make_updates(sgd)
-        cdef Beam beam
-        for beam in beams:
-            _beam_utils.cleanup_beam(beam)
 
     def _init_gold_batch(self, whole_docs, whole_golds, min_length=5, max_length=500):
         """Make a square batch, of length equal to the shortest doc. A long