Bump coverlet.msbuild from 6.0.3 to 6.0.4 in /ImperatorToCK3.UnitTests

Bumps [coverlet.msbuild](https://github.com/coverlet-coverage/coverlet) from 6.0.3 to 6.0.4.
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](coverlet-coverage/coverlet@v6.0.3...v6.0.4)

---
updated-dependencies:
- dependency-name: coverlet.msbuild
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

ImperatorToCK3.UnitTests/ImperatorToCK3.UnitTests.csproj

@@ -12,7 +12,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.msbuild" Version="6.0.3">
+    <PackageReference Include="coverlet.msbuild" Version="6.0.4">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>