Incorporated vamsimanohar username change. (opensearch-project#3231)

Signed-off-by: Jialiang Liang <jiallian@amazon.com>

Author: RyanL1997

MAINTAINERS.md

@@ -16,7 +16,7 @@ This document contains a list of maintainers in this repo. See [opensearch-proje
 | Peter Fitzgibbons | [pjfitzgibbons](https://github.com/pjfitzgibbons)   | Amazon      |
 | Simeon Widdis     | [swiddis](https://github.com/swiddis)               | Amazon      |
 | Chen Dai          | [dai-chen](https://github.com/dai-chen)             | Amazon      |
-| Vamsi Manohar     | [vamsi-amazon](https://github.com/vamsi-amazon)     | Amazon      |
+| Vamsi Manohar     | [vamsimanohar](https://github.com/vamsimanohar)     | Amazon      |
 | Peng Huo          | [penghuo](https://github.com/penghuo)               | Amazon      |
 | Sean Kao          | [seankao-az](https://github.com/seankao-az)         | Amazon      |
 | Anirudha Jadhav   | [anirudha](https://github.com/anirudha)             | Amazon      |