handle conflict errors from run service (#2570)

* handle conflict errors from run service

* nit: formatting

* fix formatting

src/Sdk/RSWebApi/RunServiceHttpClient.cs

@@ -86,6 +86,8 @@ namespace GitHub.Actions.RunService.WebApi
             {
                 case HttpStatusCode.NotFound:
                     throw new TaskOrchestrationJobNotFoundException($"Job message not found: {messageId}");
+                case HttpStatusCode.Conflict:
+                    throw new TaskOrchestrationJobAlreadyAcquiredException($"Job message already acquired: {messageId}");
                 default:
                     throw new Exception($"Failed to get job message: {result.Error}");
             }