Fix domain/codomain of MPODerivativeOperator

[20akshay00]

One-line fix to resolve #369.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/algorithms/derivatives/mpo_derivatives.jl	0.00%	2 Missing ⚠️

Files with missing lines	Coverage Δ
src/algorithms/derivatives/mpo_derivatives.jl	67.34% <0.00%> (ø)

... and 6 files with indirect coverage changes

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