Bump Akka.Cluster.Hosting in /src/reliability/rabbitmq-backpressure

Bumps [Akka.Cluster.Hosting](https://github.com/akkadotnet/Akka.Hosting) from 1.5.15 to 1.5.18.
- [Release notes](https://github.com/akkadotnet/Akka.Hosting/releases)
- [Changelog](https://github.com/akkadotnet/Akka.Hosting/blob/dev/RELEASE_NOTES.md)
- [Commits](akkadotnet/Akka.Hosting@1.5.15...1.5.18)

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

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

src/Directory.Build.props

@@ -18,7 +18,7 @@
     <TestSdkVersion>17.6.0</TestSdkVersion>
     <AkkaVersion>1.5.15</AkkaVersion>
     <PbmVersion>1.3.2</PbmVersion>
-    <AkkaHostingVersion>1.5.15</AkkaHostingVersion>
+    <AkkaHostingVersion>1.5.18</AkkaHostingVersion>
     <MicrosoftExtensionsVersion>[7.0.0,)</MicrosoftExtensionsVersion>
   </PropertyGroup>
   <!-- SourceLink support for all Akka.NET projects -->