Remove the IDE* rule duplicates after .NET 9 (OSOE-896)

[Piedone]

For code style rules we have both IDE* configs and dotnet_style_* ones. This is because only the IDE ones are honored by the build (i.e. not just the IDE), see dotnet/roslyn#44201. After dotnet/roslyn#52991, the upcoming .NET 9 has support for the dotnet_style_* rules too, see dotnet/roslyn#52991 (comment).

With <AnalysisLevel>9.0</AnalysisLevel> when upgrading to .NET 9 this should be enabled by defaullt. Verify this is the case and remove the duplicate rules.

Jira issue