Bump Confluent.Kafka from 2.6.1 to 2.8.0

Bumps [Confluent.Kafka](https://github.com/confluentinc/confluent-kafka-dotnet) from 2.6.1 to 2.8.0.
- [Release notes](https://github.com/confluentinc/confluent-kafka-dotnet/releases)
- [Changelog](https://github.com/confluentinc/confluent-kafka-dotnet/blob/master/CHANGELOG.md)
- [Commits](confluentinc/confluent-kafka-dotnet@v2.6.1...v2.8.0)

---
updated-dependencies:
- dependency-name: Confluent.Kafka
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/Foundatio.Kafka/Foundatio.Kafka.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <ItemGroup>
-    <PackageReference Include="Confluent.Kafka" Version="2.6.1" />
+    <PackageReference Include="Confluent.Kafka" Version="2.8.0" />
 
     <PackageReference Include="Foundatio" Version="11.0.6" Condition="'$(ReferenceFoundatioSource)' == '' OR '$(ReferenceFoundatioSource)' == 'false'" />
     <ProjectReference Include="..\..\..\Foundatio\src\Foundatio\Foundatio.csproj" Condition="'$(ReferenceFoundatioSource)' == 'true'" />