[ENH] Update VARMAX pandas 2.0

[AnonymousCodes911]

updated pandas version to 2.0

Reference Issues/PRs

#291

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I have added the following labels to this PR based on the title: [ $\color{#FEF1BE}{\textsf{enhancement}}$ ].
I have added the following labels to this PR based on the changes made: [ $\color{#31FCCD}{\textsf{forecasting}}$ ]. Feel free to change these if they do not properly represent the PR.

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[AnonymousCodes911]

@MatthewMiddlehurst, is this change a fix?, or should we deprecate certain functions to ensure compatibility? local Tests are currently being skipped due to the absence of soft dependencies.

[MatthewMiddlehurst]

No, this is not the fix required. You will see issues emerge if you remove the dependency line completely.

[AnonymousCodes911]

@MatthewMiddlehurst , Thanks! I will work accordingly.

[MatthewMiddlehurst]

I think it's best to leave this for now, IMO. We have some significant changes to the module planned which may make this irrelevant either way.

[AnonymousCodes911]

I see, I ll Close this for now!