Update Blazor-EF Core sample to .NET 5 RC1 (#19888)

Author: guardrex

aspnetcore/blazor/common/samples/5.x/BlazorServerEFCoreSample/BlazorServerDbContextExample/BlazorServerDbContextExample.csproj

@@ -1,11 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net5.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="5.0.0-preview.7.20365.15" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="5.0.0-rc.1.*" />
   </ItemGroup>
 
 </Project>