Fix one of the tests

[marwahaha]

There is an issue with one of the tests @jbroz11
constants -- other constants | 7 7 0.1s

operators -- VibrationalMode operators: Test Failed at /home/runner/work/IonSim.jl/IonSim.jl/test/test_operators.jl:34

Expression: ≈((displace(modes[1], α, method = "analytic")).data[i, j], (qo.displace(fb2, α)).data[i, j], rtol = 0.001)

Evaluated: 1.028639165911405e-15 - 1.0043267489904697e-15im ≈ 1.0933935056671732e-15 - 9.23343098384506e-16im (rtol=0.001)

[marwahaha]

Can't find an example. Let's try again when it fails again.