Adjust to nullable annotations of ContextBag

Author: danielmarbach

src/NServiceBus.Storage.MongoDB/SynchronizedStorage/StorageSession.cs

@@ -112,9 +112,9 @@ public async Task AbortTransaction(CancellationToken cancellationToken = default
         }
     }
 
-    public void StoreVersion<T>(int version) => contextBag.Set(typeof(T).FullName, version);
+    public void StoreVersion<T>(int version) => contextBag.Set(typeof(T).FullName!, version);
 
-    public int RetrieveVersion(Type type) => contextBag.Get<int>(type.FullName);
+    public int RetrieveVersion(Type type) => contextBag.Get<int>(type.FullName!);
 
     public Task CommitTransaction(CancellationToken cancellationToken = default)
     {