chore: remove aws sdk core dep

Author: Shubham Chaturvedi

DynamoDbEncryption/runtimes/net/DynamoDbEncryption.csproj

@@ -58,7 +58,6 @@
 
   <ItemGroup>
     <PackageReference Include="AWSSDK.DynamoDBv2" Version="3.7.402.2"/>
-    <PackageReference Include="AWSSDK.Core" Version="3.7.400.38"/>
     <PackageReference Include="DafnyRuntime" Version="$(DafnyVersion)" />
     <ProjectReference Include="../../../submodules/MaterialProviders/AwsCryptographicMaterialProviders/runtimes/net/MPL.csproj"/>
     <!--