[project-history] fix name for error in logging statement (#23110)

Only the err/error fields will use the Error serializer and emit all the
OError details into the log.

GitOrigin-RevId: 4b0e16c00be5ea7c0aea747f49b46897ebd100cc

services/project-history/app/js/FlushManager.js

@@ -106,7 +106,7 @@ export function flushOldOps(options, callback) {
                 return flushIfOld(projectId, cutoffTime, function (err) {
                   if (err != null) {
                     logger.warn(
-                      { projectId, flushErr: err },
+                      { projectId, err },
                       'error flushing old project'
                     )
                   }