build(deps): bump ICSharpCode.Decompiler from 7.2.1.6856 to 8.1.0.7455

Bumps [ICSharpCode.Decompiler](https://github.com/icsharpcode/ILSpy) from 7.2.1.6856 to 8.1.0.7455.
- [Release notes](https://github.com/icsharpcode/ILSpy/releases)
- [Changelog](https://github.com/icsharpcode/ILSpy/blob/master/releasebuild.bat)
- [Commits](https://github.com/icsharpcode/ILSpy/commits)

---
updated-dependencies:
- dependency-name: ICSharpCode.Decompiler
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

src/ReactiveMarbles.ObservableEvents.Tests/ReactiveMarbles.ObservableEvents.Tests.csproj

@@ -21,7 +21,7 @@
     </PackageReference>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="3.11.0" />
     <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
-    <PackageReference Include="ICSharpCode.Decompiler" Version="7.2.1.6856" />
+    <PackageReference Include="ICSharpCode.Decompiler" Version="8.1.0.7455" />
     <PackageReference Include="ReactiveMarbles.NuGet.Helpers" Version="1.0.33" />
   </ItemGroup>