Bump AkkaVersion from 1.4.39 to 1.4.40 (#258)

Bumps `AkkaVersion` from 1.4.39 to 1.4.40.

Updates `Akka.Persistence.Sql.Common` from 1.4.39 to 1.4.40
- [Release notes](https://github.com/akkadotnet/akka.net/releases)
- [Changelog](https://github.com/akkadotnet/akka.net/blob/1.4.40/RELEASE_NOTES.md)
- [Commits](akkadotnet/akka.net@1.4.39...1.4.40)

Updates `Akka.Persistence.Sql.TestKit` from 1.4.39 to 1.4.40
- [Release notes](https://github.com/akkadotnet/akka.net/releases)
- [Changelog](https://github.com/akkadotnet/akka.net/blob/1.4.40/RELEASE_NOTES.md)
- [Commits](akkadotnet/akka.net@1.4.39...1.4.40)

---
updated-dependencies:
- dependency-name: Akka.Persistence.Sql.Common
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Akka.Persistence.Sql.TestKit
  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/common.props

@@ -13,7 +13,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <XunitVersion>2.4.1</XunitVersion>
-    <AkkaVersion>1.4.39</AkkaVersion>
+    <AkkaVersion>1.4.40</AkkaVersion>
     <TestSdkVersion>17.2.0</TestSdkVersion>
     <NetCoreTestVersion>netcoreapp3.1</NetCoreTestVersion>
     <NetFrameworkTestVersion>net461</NetFrameworkTestVersion>