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

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src/qibolab/serialize.py

@@ -23,7 +23,7 @@
     QubitPairMap,
     Settings,
 )
-from qibolab.pulses import Delay, Pulse, PulseSequence, PulseType, VirtualZ
+from qibolab.pulses import Pulse, PulseSequence, PulseType
 from qibolab.pulses.pulse import PulseLike
 from qibolab.qubits import Qubit, QubitPair