docs: fix simple typo, sigificant -> significant (#3631)
docs: fix simple typo, sigificant -> significant (#3631)

There is a small typo in cirq/experiments/fidelity_estimation.py.

Should read `significant` rather than `sigificant`.


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https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md
quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,balopat/Cirq,quantumlib/Cirq,balopat/Cirq,quantumlib/Cirq,balopat/Cirq