Fixes order of arguments for some Hessian methods for priors

[evgueni-ovtchinnikov]

Changes in this pull request

Testing performed

Related issues

fixes #1343

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• I have performed a self-review of my code
• I have added docstrings/doxygen in line with the guidance in the developer guide
• I have implemented unit tests that cover any new or modified functionality
• The code builds and runs on my machine
• CHANGES.md has been updated with any functionality change

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