Bump Akka.Cluster.TestKit from 1.5.2 to 1.5.6 (#178)

Bumps [Akka.Cluster.TestKit](https://github.com/akkadotnet/akka.net) from 1.5.2 to 1.5.6.
- [Release notes](https://github.com/akkadotnet/akka.net/releases)
- [Changelog](https://github.com/akkadotnet/akka.net/blob/dev/RELEASE_NOTES.md)
- [Commits](akkadotnet/akka.net@1.5.2...1.5.6)

---
updated-dependencies:
- dependency-name: Akka.Cluster.TestKit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/common.props

@@ -24,7 +24,7 @@
     <NetStandardLibVersion>netstandard2.0</NetStandardLibVersion>
     <FluentAssertionsVersion>6.6.0</FluentAssertionsVersion>
     <FsCheckVersion>2.16.5</FsCheckVersion>
-    <AkkaVersion>1.5.2</AkkaVersion>
+    <AkkaVersion>1.5.6</AkkaVersion>
     <AkkaPackageTags>akka;actors;actor model;Akka;concurrency</AkkaPackageTags>
   </PropertyGroup>
   <PropertyGroup>