Bump coverlet.collector from 3.1.2 to 6.0.2 in /csharp/src

Bumps [coverlet.collector](https://github.com/coverlet-coverage/coverlet) from 3.1.2 to 6.0.2.
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](https://github.com/coverlet-coverage/coverlet/commits/v6.0.2)

---
updated-dependencies:
- dependency-name: coverlet.collector
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

csharp/tests/Base64EncoderTests/Base64EncoderTests.csproj

@@ -10,7 +10,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
     <PackageReference Include="MSTest.TestAdapter" Version="2.2.10" />
     <PackageReference Include="MSTest.TestFramework" Version="2.2.10" />
-    <PackageReference Include="coverlet.collector" Version="3.1.2" />
+    <PackageReference Include="coverlet.collector" Version="6.0.2" />
   </ItemGroup>
 
   <ItemGroup>

csharp/tests/HKDFTests/HKDFTests.csproj

@@ -10,7 +10,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
     <PackageReference Include="MSTest.TestAdapter" Version="2.2.10" />
     <PackageReference Include="MSTest.TestFramework" Version="2.2.10" />
-    <PackageReference Include="coverlet.collector" Version="3.1.2" />
+    <PackageReference Include="coverlet.collector" Version="6.0.2" />
   </ItemGroup>
 
   <ItemGroup>