Potential fix for code scanning alert no. 1: Missing Dispose call on local IDisposable (#21)

Potential fix for
[https://github.com/AzureCosmosDB/samples/security/code-scanning/1](https://github.com/AzureCosmosDB/samples/security/code-scanning/1)

In general, the correct fix is to ensure that any object implementing
`IDisposable` is disposed, preferably via a `using` statement/`using`
declaration so that disposal happens automatically when the scope ends,
even if exceptions occur. For a short, top-level sample like this, the
most straightforward change is to wrap the `CosmosClient` creation in a
`using` declaration so that it is disposed when the program reaches the
end of the top-level scope.

Concretely, in `dotnet/001-connect-passwordless/connect.cs`, change the
line that creates `client` from a plain `var client = new
CosmosClient(endpoint, credential);` to a `using var client = new
CosmosClient(endpoint, credential);`. This keeps all existing behavior
the same while ensuring `Dispose` is called when the top-level
statements complete. No additional methods or imports are required;
`using var` is a C# language feature and `CosmosClient` already
implements `IDisposable`.


_Suggested fixes powered by Copilot Autofix. Review carefully before
merging._

Signed-off-by: Sidney Andrews <sidandrews@microsoft.com>
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: seesharprun

dotnet/001-connect-passwordless/connect.cs

@@ -12,7 +12,7 @@
     ?? throw new InvalidOperationException("COSMOS_ENDPOINT is not configured. Run: dotnet user-secrets set --file connect.cs \"COSMOS_ENDPOINT\" \"<your-endpoint>\"");
 
 var credential = new DefaultAzureCredential();
-var client = new CosmosClient(endpoint, credential);
+using var client = new CosmosClient(endpoint, credential);
 
 AccountProperties account = await client.ReadAccountAsync();
 Console.WriteLine($"Account: {account.Id}");