Deprecation Warnings

[uniblab]

Hi.

I'm announcing a future-fix in PR #611 .

In a recent PR, I updated the build targets to also emit .Net 7.0+. This triggered a few compiler warnings in all the Exception classes because they override and implement members which were recently tagged with the Obsolete attribute. This PR takes care of those warnings by molly-guarding an Obsolete attribute where necessary in NET8_0_OR_GREATER as is proper.

This doesn't hurt anything in the current build targets but does cure the compiler warnings when PR #610 is approved and merged.

Thanks for reviewing the PR!

[peterdettman]

Redundant with #611 .