Bump AkkaVersion from 1.5.12 to 1.5.13 (#266)

Bumps `AkkaVersion` from 1.5.12 to 1.5.13.

Updates `Akka` from 1.5.12 to 1.5.13
- [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@1.5.12...1.5.13)

Updates `Akka.TestKit.Xunit2` from 1.5.12 to 1.5.13
- [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@1.5.12...1.5.13)

Updates `Akka.Cluster` from 1.5.12 to 1.5.13
- [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@1.5.12...1.5.13)

---
updated-dependencies:
- dependency-name: Akka
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Akka.TestKit.Xunit2
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Akka.Cluster
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/Directory.Build.props

@@ -12,7 +12,7 @@
     <LangVersion>10</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
-    <AkkaVersion>1.5.12</AkkaVersion>
+    <AkkaVersion>1.5.13</AkkaVersion>
     <AkkaHostingVersion>1.5.12.1</AkkaHostingVersion>
     <NetCoreTestVersion>netcoreapp3.1</NetCoreTestVersion>
     <NetFrameworkTestVersion>net471</NetFrameworkTestVersion>