Bump AWSSDK.Core from 3.7.400.16 to 3.7.400.20

Bumps [AWSSDK.Core](https://github.com/aws/aws-sdk-net) from 3.7.400.16 to 3.7.400.20.
- [Changelog](https://github.com/aws/aws-sdk-net/blob/main/SDK.CHANGELOG.MD)
- [Commits](https://github.com/aws/aws-sdk-net/commits)

---
updated-dependencies:
- dependency-name: AWSSDK.Core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

src/OpenSearch.Net.Auth.AwsSigV4/OpenSearch.Net.Auth.AwsSigV4.csproj

@@ -20,6 +20,6 @@
     <ProjectReference Include="$(SolutionRoot)\src\OpenSearch.Net\OpenSearch.Net.csproj" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="AWSSDK.Core" Version="3.7.400.16" />
+    <PackageReference Include="AWSSDK.Core" Version="3.7.400.20" />
   </ItemGroup>
 </Project>