Bump System.Data.SqlClient from 4.7.0 to 4.8.0

Bumps [System.Data.SqlClient](https://github.com/dotnet/corefx) from 4.7.0 to 4.8.0.
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

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

src/Akka.Persistence.SqlServer/Akka.Persistence.SqlServer.csproj

@@ -23,7 +23,7 @@
 
   <ItemGroup Condition="'$(TargetFramework)' == '$(NetStandardLibVersion)'">
     <PackageReference Include="System.Data.SqlClient">
-      <Version>4.7.0</Version>
+      <Version>4.8.0</Version>
     </PackageReference>
   </ItemGroup>
 </Project>