Add missing ConfigureAwait on awaited task.

Author: David Ellingsworth

src/RestSharp/AsyncHelpers.cs

@@ -45,7 +45,7 @@ static void RunSync(Func<Task> task) {
     /// <returns>Return value from the task</returns>
     public static T RunSync<T>(Func<Task<T>> task) {
         T result = default!;
-        RunSync(async () => { result = await task(); });
+        RunSync(async () => { result = await task().ConfigureAwait(false); });
         return result;
     }