fix(ConfigurableMessageHandler): Clear quota project header on retry

Author: robertvoinescu-work

Src/Support/Google.Apis.Core/Http/ConfigurableMessageHandler.cs

@@ -641,6 +641,13 @@ bool DisposeAndReturnFalse(IDisposable disposable)
                         }
                     }
                 }
+
+                if (triesRemaining > 0)
+                {
+                    // The request object was modifed and needs to be cleaned up before retries, in particular the Quota Project 
+                    // header must be unset so we can apply a fresh value.
+                    request.Headers.Remove(QuotaProjectHeaderName);
+                }
             } while (triesRemaining > 0); // Not a successful status code but it was handled.
 
             // If the response is null, we should throw the last exception.