fix: Fixed Postgres update issue.

Author: HavenDV

src/Utilities/Postgres/src/LangChain.Utilities.Postgres.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFrameworks>net4.6.2;netstandard2.0;net8.0;net9.0</TargetFrameworks>
+        <TargetFrameworks>net8.0;net9.0</TargetFrameworks>
         <NoWarn>$(NoWarn);CA1031;CA2100;CA1305</NoWarn>
     </PropertyGroup>