Update code to remove use of deprecated PluginCustomValidator class.

[nrnvgh]

Closes: #181

What's Changed

• Replaced all uses of PluginCustomValidator with CustomValidator to clean up deprecation warnings
• Lint fixup on logger statement.

To Do

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)
• Attached Screenshots, Payload Example
• Unit, Integration Tests
• Documentation Updates (when adding/changing features)
• Outline Remaining Work, Constraints from Design

[glennmatthews]

Thanks! Note that this app is slated to be inlined into Nautobot core in the v3.0 release (see nautobot/nautobot#6866 and following pull requests), but it doesn't hurt to clean it up for 2.x in the meanwhile.

[nrnvgh]

Checking in on this. Zero rush on my side, it's just been a couple of weeks is all.