[pre-commit.ci] auto fixes from pre-commit.com hooks

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src/qibo/hamiltonians/hamiltonians.py

@@ -180,7 +180,7 @@ def energy_fluctuation(self, state):
         energy = self.expectation(state)
         h = self.matrix
         h2 = Hamiltonian(nqubits=self.nqubits, matrix=h @ h, backend=self.backend)
-        average_h2 = h2.expectation( state, normalize=True)
+        average_h2 = h2.expectation(state, normalize=True)
         return np.sqrt(np.abs(average_h2 - energy**2))
 
     def __add__(self, o):