removed mention of toffoli method which doesn't exist anymore (#14080)

Author: LenaPer

qiskit/circuit/library/standard_gates/x.py

@@ -301,8 +301,7 @@ class CCXGate(SingletonControlledGate):
     r"""CCX gate, also known as Toffoli gate.
 
     Can be applied to a :class:`~qiskit.circuit.QuantumCircuit`
-    with the :meth:`~qiskit.circuit.QuantumCircuit.ccx` and
-    :meth:`~qiskit.circuit.QuantumCircuit.toffoli` methods.
+    with the :meth:`~qiskit.circuit.QuantumCircuit.ccx` method.
 
     **Circuit symbol:**