Bump RestSharp from 106.13.0 to 106.15.0

Bumps [RestSharp](https://github.com/restsharp/RestSharp) from 106.13.0 to 106.15.0.
- [Release notes](https://github.com/restsharp/RestSharp/releases)
- [Commits](restsharp/RestSharp@106.13.0...106.15.0)

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

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

Akismet.Net/Akismet.Net.csproj

@@ -20,7 +20,7 @@
 
   <ItemGroup>
     <PackageReference Include="RestSharp">
-      <Version>106.13.0</Version>
+      <Version>106.15.0</Version>
     </PackageReference>
     <PackageReference Include="Newtonsoft.Json">
       <Version>13.0.3</Version>