Avoid sending update/delete release notice when it is draft (#29008) (#29025)

Backport #29008 by @yp05327

Fix #27157

Co-authored-by: yp05327 <576951401@qq.com>

services/release/release.go

 		}
 	}
 
-	if !isCreated {
-		notify_service.UpdateRelease(gitRepo.Ctx, doer, rel)
-		return nil
-	}
-
 	if !rel.IsDraft {
+		if !isCreated {
+			notify_service.UpdateRelease(gitRepo.Ctx, doer, rel)
+			return nil
+		}
 		notify_service.NewRelease(gitRepo.Ctx, rel)
 	}
-
 	return nil
 }
 
 		}
 	}
 
-	notify_service.DeleteRelease(ctx, doer, rel)
-
+	if !rel.IsDraft {
+		notify_service.DeleteRelease(ctx, doer, rel)
+	}
 	return nil
 }