[AC-1980] Upgrade Stripe.net (#3596)

* Upgrade Stripe.net

* Don't process mismatched version webhooks

* Manually handle API mismatch in Stripe webhook

* Pivot webhook secret off webhook version

src/Billing/Models/StripeWebhookVersionContainer.cs

@@ -0,0 +1,9 @@
+using System.Text.Json.Serialization;
+
+namespace Bit.Billing.Models;
+
+public class StripeWebhookVersionContainer
+{
+    [JsonPropertyName("api_version")]
+    public string ApiVersion { get; set; }
+}