Revert "Add missing ConfigureAwait on awaited task."

The anonymous method in the RunSync call does not capture the
current context until it is executed. Because it is called
from within the CustomSynchronizationContext, it will always capture
the CustomSynchhronizationContext and not the caller's context.

This reverts commit ec15969.

Author: David Ellingsworth

src/RestSharp/AsyncHelpers.cs

@@ -38,7 +38,7 @@ 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().ConfigureAwait(false); });
+        RunSync(async () => { result = await task(); });
         return result;
     }