Remove argument decomposer from constructor of ConsolidateBlocks

This was added in a previous commit in the series of commits for this
PR. The code has been redesigned so that this argument is no longer
necessary.

qiskit/transpiler/passes/optimization/consolidate_blocks.py

@@ -49,20 +49,19 @@ def __init__(
         basis_gates=None,
         approximation_degree=1.0,
         target=None,
-        decomposer=None,
     ):
         """ConsolidateBlocks initializer.
 
-        The decomposer used is determined by the first of the following arguments
-        with a non-None value: decomposer, kak_basis_gate, basis_gates. If all are None,
+        The decomposer used is kak_basis_gate if it has non-None value. Otherwise
+        the decomposer is basis_gates if it has non-None value. If both are None,
         then a default decomposer is used.
+
         Args:
             kak_basis_gate (Gate): Basis gate for KAK decomposition.
             force_consolidate (bool): Force block consolidation.
             basis_gates (List(str)): Basis gates from which to choose a KAK gate.
             approximation_degree (float): a float between [0.0, 1.0]. Lower approximates more.
             target (Target): The target object for the compilation target backend.
-            decomposer: A 2q gate decomposer.
         """
         super().__init__()
         self.basis_gates = None
@@ -71,8 +70,6 @@ def __init__(
             self.basis_gates = set(basis_gates)
         self.force_consolidate = force_consolidate
 
-        if decomposer is not None:
-            self.decomposer = decomposer
         if kak_basis_gate is not None:
             self.decomposer = TwoQubitBasisDecomposer(kak_basis_gate)
         elif basis_gates is not None: