Revert "Temp upgrade to Npgsql 10.0.0.0 for net8"

This reverts commit 8883711.

Author: alex-kulakov

Orm/Xtensive.Orm.PostgreSql/Xtensive.Orm.PostgreSql.csproj

@@ -24,15 +24,9 @@
       <Visible>false</Visible>
     </Content>
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net6.0'">
-    <PackageReference Include="Npgsql" Version="9.0.4" />
-  </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net7.0'">
+  <ItemGroup>
     <PackageReference Include="Npgsql" Version="9.0.4" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net8.0'">
-    <PackageReference Include="Npgsql" Version="10.0.0" />
-  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Xtensive.Orm\Xtensive.Orm.csproj" />
   </ItemGroup>

Orm/Xtensive.Orm.Tests/Xtensive.Orm.Tests.csproj

@@ -18,18 +18,9 @@
   <ItemGroup Condition="'$(TargetFramework)'=='net7.0' OR '$(TargetFramework)'=='net8.0'">
     <PackageReference Include="System.Configuration.ConfigurationManager" Version="8.0.0" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net6.0'">
-    <PackageReference Include="Npgsql" Version="9.0.4" />
-  </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net7.0'">
-    <PackageReference Include="Npgsql" Version="9.0.4" />
-  </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)'=='net8.0'">
-    <PackageReference Include="Npgsql" Version="10.0.0" />
-  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
-    <!-- <PackageReference Include="Npgsql" Version="9.0.4" /> -->
+    <PackageReference Include="Npgsql" Version="9.0.4" />
     <PackageReference Include="NUnit" Version="3.13.2" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.2.0" />
     <PackageReference Include="System.CodeDom" Version="4.4.0" />