Add release note for the informer cache memory consumption

Add release note for the informer cache memory consumption

Signed-off-by: Wenkai Yin(尹文开) <yinw@vmware.com>

changelogs/CHANGELOG-1.13.md

@@ -64,6 +64,9 @@ To fix CVEs and keep pace with Golang, Velero made changes as follows:
 ### Limitations/Known issues
 * The backup's VolumeInfo metadata doesn't have the information updated in the async operations. This function could be supported in v1.14 release. 
 
+### Note
+* Velero introduces the informer cache which is enabled by default. The informer cache improves the restore performance but may cause higher memory consumption. Increase the memory limit of the Velero pod or disable the informer cache by specifying the `--disable-informer-cache` option when installing Velero if you get the OOM error.
+
 ### Deprecation announcement
 * The generated k8s clients, informers, and listers are deprecated in the Velero v1.13 release. They are put in the Velero repository's pkg/generated directory. According to the n+2 supporting policy, the deprecated are kept for two more releases. The pkg/generated directory should be deleted in the v1.15 release.
 * After the backup VolumeInfo metadata file is added to the backup, Velero decides how to restore the PV resource according to the VolumeInfo content. To support the backup generated by the older version of Velero, the old logic is also kept. The support for the backup without the VolumeInfo metadata file will be kept for two releases. The support logic will be deleted in the v1.15 release.