Relax Node.js version to ^14.20.1 and bump .nvmrc to v14.21.3

* `engines.node` is relaxed from `14.20.1` to `^14.20.1`: yarn and OSD will allow versions 14.20.1 or greater, but less than 15, to be used but do not impose upgrading to avoid being a breaking change. Users will be able to install any version of Node.js that satisfies `^14.20.1`, moving ahead without waiting for a change in OSD when new versions are released.
* `.nvmrc` is bumped to the latest security patch: `14.21.3`

Signed-off-by: Miki <miki@amazon.com>

.nvmrc

@@ -1 +1 @@
-14.20.1
+14.21.3

CHANGELOG.md

@@ -132,6 +132,8 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Bumps `re2` and `supertest` ([3018](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/3018))
 - Bump `vega-tooltip` version from ^0.24.2 to ^0.30.0 ([#3358](https://github.com/opensearch-project/OpenSearch-Dashboards/issues/3358))
 - Allow relaxing the Node.js runtime version requirement ([3402](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/3402))
+- Relax the Node.js requirement to `^14.20.1` ([3463](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/3463))
+- Bump the version of Node.js installed by `nvm` to `14.21.3` ([3463](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/3463))
 
 ### 🪛 Refactoring
 

package.json

@@ -466,7 +466,7 @@
     "zlib": "^1.0.5"
   },
   "engines": {
-    "node": "14.20.1",
+    "node": "^14.20.1",
     "yarn": "^1.21.1"
   }
 }