fix: src/REstate.Engine.Repositories.EntityFrameworkCore/REstate.Engine.Repositories.EntityFrameworkCore.csproj to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DOTNET-SYSTEMSECURITYCRYPTOGRAPHYX509CERTIFICATES-6618055

Author: snyk-bot

src/REstate.Engine.Repositories.EntityFrameworkCore/REstate.Engine.Repositories.EntityFrameworkCore.csproj

@@ -8,7 +8,7 @@
 
   <ItemGroup>
     <PackageReference Include="MessagePack" Version="1.9.3" />
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="2.1.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="3.1.0" />
     <PackageReference Include="System.Data.SqlClient" Version="4.5.1" />
   </ItemGroup>